10.48255/1973-9494.JCSCH.21.2021.15
L’architettura della sottrazione inserita nel paesaggio rurale è una tipologia di architettura che ha avuto, per la società rurale, una importante valenza economica e culturale fino al XX secolo. La conoscenza, la catalogazione, la conservazione e la valorizzazione dell’architettura della sottrazione diventano, quindi, fondamentali per preservare la cultura e il paesaggio rurale del centro Italia. L’articolo presenta e cataloga tale tipologia di architettura e propone un progetto, finalizzato al recupero e alla valorizzazione di alcuni siti scavati abbandonati e degradati, per la realizzazione di un Museo diffuso della civiltà contadina e artigiana dei secoli XIX e XX.
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The architecture of subtraction in the rural landscape of central Italy: conservation and valorization
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Maria Letizia De Luca
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The architecture of subtraction in the rural landscape of central Italy: conservation and valorization
https://conservation-science.unibo.it/article/download/15257/14486
21
T    HE ARCHITECTURE OF SUBTRACTION IN THE RURAL
     LANDSCAPE OF CENTRAL ITALY: CONSERVATION AND
     VALORIZATION


   Andrea Natali * 1




   Conservazione beni culturali, Viterbo, Italy

   Maria Letizia De Luca
   Ordine degli Architetti e Paesaggisti di Roma e Provincia, Italy

   Keywords: architecture, conservation, valorization, architectural heritage

   DOI: 10.48255/1973-9494.JCSCH.21.2021.15




   1. Introduction

    “By sculpture I mean that which is fashioned by the effort of cutting away”. This
statement by Michelangelo Buonarroti (1475 – 1564) expresses the platonic concept
of the preexisting idea trapped within the constraint of the block from which the artist
has to set it free by removing the excess (covering). The sentence also communi-
cates another concept, which is the struggle between the man and the rock that has
to be tamed and “obey the intellect” [1].
    Leon Battista Alberti in “De statua”, a treatise written in 1462 on the theory of sculp-
ture, had already classified it as either “adding” or “removing”, depending on the tech-
nique that was used. Michelangelo, painter, architect and writer, who considered him-
self above all a sculptor, takes up this classification and going to extremes states that
sculpting is done by “cutting away” and not by “adding” as happens, instead, with paint-
ing, clay modeling and bronze statues.
    The sculptor eliminates the material that hides the shape, as the latter is already
ideally present in the rock: their task is to reveal it, through manual labor that is, at the
same time, a process of the intellect and of the spirit. The idea is already there even
before the creative act takes place; it is the artist’s task to make it visible [2].
    As in the architecture of subtraction the idea of the environment to be obtained by
carving it out is already there and is “easy” to shape with effort and time: concepts that
until the middle of the twentieth century were not valued as they are today.
    And it is exactly with this perspective in mind that the designer-creator-maker act-
ed. The utensils were few and simple: a pick, wedges and a shovel.
    This is why it was more convenient to excavate a cellar, a storeroom or a well, com-
pared to constructing by adding, since the materials (mortars, beams, shingles, etc.)
were expensive, not to mention the time and effort that was needed.




   * Corresponding author: andreanatali.beniculturali@gmail.com
                                                                                                                                      2. The architecture of subtraction

                                                                                                                                       Negative architecture, passive architecture, underground architecture, subtractive
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   architecture are all terms that refer to the architectural technique in which you do not
                                                                                                                                   build but take material away from the rock to obtain spaces simply by carving it, in oth-
                                                                                                                                   er words by cutting away, forcefully or artfully taking away, removing. For this paper, it
                                                                                                                                   was decided that the term subtractive architecture would be used to refer to enclosures
                                                                                                                                   obtained by cutting away and removing material from an existing volume, as well as to
                                                                                                                                   conform to other authors. This underlines the intentionality of the act of subtracting, in
                                                                                                                                   the same way architecture built on the surface is the result of an act of adding, that is,
                                                                                                                                   of the assembly and addition of materials. [3]
                                                                                                                                       Subtractive architecture was born as a result of chiseling the natural landscape to
                                                                                                                                   then blend in with it, so it becomes an integral part of it. It communicates with the sur-
                                                                                                                                   face of which it is a natural extension. Therefore, it does not stand alone confined to a
                                                                                                                                   space in the ground. The difference is evident, positive architecture is additive, since it
                                                                                                                                   exists in an environmental context as an added object and is for this reason recogniza-
                                                                                                                                   ble, distinguishable, and in many cases invasive. [4]
                                                                                                                                       Research takes into consideration only some types of subtractive architecture for the
                                                                                                                                   purpose of study and photo cataloguing, that is to say, it considers a type of subtractive
                                                                                                                                   architecture that has no definable historical or archeological characteristics and, at least
                                                                                                                                   on paper, has not yet been considered as needing protection, as in the case of sepul-
                                                                                                                                   chers (unless they have recently been adaptively re-used for a new scope) or the well-
                                                                                                                                   known Sassi di Matera, registered on the list of Unesco World Heritage Sites in 1993.
                                                                                                                                       Interest, therefore, derives from different issues.
                                                                                                                                       The redevelopment and/or eventual reuse of these types of architecture up to re-
                                                                                                                                   cent times (there are very few cases relating to current day uses or continued use over
                                                                                                                                   the centuries) has enabled us to understand how the territory was used.
                                                                                                                                       These environments are evidence of a considerable piece of history, culture and
                                                                                                                                   society that the territory has experienced and continues to experience. They recall
                                                                                                                                   matters relating to daily life and working conditions, because until a few decades ago
                                                                                                                                   they were inhabited and used. An evocative painting from the 1940s by the artist Pietro
                                                                                                                                   Canonica, who was appointed Senator for life of the Italian Republic for artistic merits,
                                                                                                                                   portrays this reality: the title “Case nel tufo” (houses hewn in the tuff rock) is unequivo-
                                                                                                                                   cal in showing how these environments were used (Figure 1).
                                                                                                                                       However, it should be noted that very few excavated structures made centuries ago
                                                                                                                                   to serve a specific purpose stayed that way through the years and were still in use in
                                                                                                                                   the 1900s. Therefore, the paper looks at excavated structures that were still being
                                                                                                                                   used in the 20th century, and usually include storerooms, cellars, shelters or stables, al-
                                                                                                                                   though they may originally have had a different function: from the reused Etruscan sep-
                                                                                                                                   ulcher (as in the case of Grotta porcina in Vetralla in the province of Viterbo, an Etruscan
                                                                                                                                   tomb which, as its name suggests, was converted into shelters for pigs and, later, as a
                                                                                                                                   storage space for agricultural vehicles) to new constructions, such as the cellars in
                                                                                                                                   urban centers, the quarries for extracting construction materials, the wartime shelters
                                                                                                                                   and stretches of road.
                                                                                                                                       The idea is to propose a different point of view (an original one), where instead of
                                                                                                                                   the original function of the place, preference is given to its reuse, seen as an expression
                                                                                                                                   not just of one civilization but of all the civilizations that have utilized these places up
                                                                                                                                   to the present day. The approach, therefore, not only relates to archeology, understood
                                                                                                                                   as the science that studies civilizations and human cultures of the past and their re-


                                                                                                 318
lationship with the surrounding environment, through the collection, the documentation
and the analysis of the material traces they have left behind (in this case the architec-
ture), but also and especially to anthropology and the history of rural farming culture
which, unless it is passed on, risks falling into oblivion.
     The passage from the 1800s to the 1900s is a period of transition: the basins made
for macerating the hemp and flax used to make ropes (where few traces of its produc-
tion remain, if not in the local toponymy: in Vetralla, the street named Via dei Funari,
meaning rope-makers, still exists) and textiles, start being built in stone.
     Most Etruscan and Roman canals and aqueducts have been abandoned. During
the Middle Ages some were reused for other purposes (sections of aqueducts became
catacombs or temporary shelters, and cisterns became churches, etc.) and some of the
ancient, excavated roads became trenches used for defense purposes; new roads were
also excavated and were documented in the 1700s, and when Tuscia became part of
the French Empire, others were excavated, and are still in use today [5].
     Sanctuaries and hermitages are still used, even though there is a risk the rock walls
may collapse, a phenomenon which inevitably occurs over the years. Some of them
have become stables.
     A sizable number of the furnaces excavated in the rock with adjacent workshops,
in particular those for the production of terracotta, operated throughout the twentieth
century: few of them continue to do so.
     The grottoes used as henhouses and several wells are still operative.
     The “Troscioni” deserve a special mention: they are retention basins of various siz-
es excavated in the woods in areas of clay soil (the clay makes the ground waterproof).
The basins, which are usually not very deep, are used for collecting rainwater and pro-
vide a water reserve also during the summertime; in the past, they were used for
free-roaming cattle breeding and today, are used by the local fauna; they are, conse-
quently, of enormous documentary, environmental and landscape interest.
     An exception has been made for the apiaries [6] and rupestrian columbaria because,




                                                                                                CONSERVATION SCIENCE IN CULTURAL HERITAGE
even though they have not been used since the nineteenth century, they are evidence of
the fundamental practices used for the provision of honey and fresh meat for the com-
munity and risk being forgotten; for this reason, their architecture needs to be preserved.
     Furthermore, for the cataloguing and, in particular, the dating of the structures and
their uses, it was necessary to address the problem of pre-existing structures.
     In the study of population dynamics, in fact, the interaction between humans and the
environment is conditioned by the pre-existence of structures of an anthropic nature.
     Hydraulic infrastructures, like road networks, are an important legacy, because their
continued use, decommissioning or eventual reuse, allow us to understand how the
territory was occupied. Water availability and water supply are essential for the survival
and development of a settlement. In particular, the reuse of these structures determines
the anthropic landscape, favoring:
   a)   uninterrupted functional continuity that some tunnels seem to have had over
        the centuries;
   b)   full decommissioning followed by a change in use;
   c) reuse connected to their functional exploitation and the development of new
      productive activities. [7]
   Another interesting aspect of excavated structures is that, since they are integrated
so well into the landscape, and almost completely camouflaged in the vegetation,
they evoke a romantic beauty, a “way of feeling/sensing” the place.


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                                                                                                                                       After all, Romanticism emerged in the eighteenth century as a reaction to the
                                                                                                                                   Enlightenment and to Neoclassicism, in other words to the rationality and cult of
                                                                                                                                   classical beauty, which counterposes the spirituality, emotionality, fantasy, imagi-
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   nation, and above all the affirmation of specific characteristics [8], in our case of ar-
                                                                                                                                   chitecture.
                                                                                                                                       No two hollowed out shapes are alike, but they evoke animal settlements such
                                                                                                                                   as termites’ or ants’ nests, badgers’ or porcupines’ dens or the birds’ nests carved
                                                                                                                                   out of clay walls such as those of the European bee-eater, the sand martin or the
                                                                                                                                   kingfisher.
                                                                                                                                       It is this integration into the rural landscape that we want to protect and preserve,
                                                                                                                                   and at least keep its memory alive.
                                                                                                                                       A return to the subterranean, a reaction to Plato who, in his Allegory of the Cave
                                                                                                                                   urges the people to leave it: “But if they were to go outside the cave and see things in the
                                                                                                                                   light of day, they would realize that they had lived in a world of appearances” and to
                                                                                                                                   Nietzsche: “God is dead: but given the way of men, there may still be caves, for thou-
                                                                                                                                   sands of years in which his shadow will be shown” to see the architecture of subtrac-
                                                                                                                                   tion as a rediscovery of the civilizations that inhabited it, and used and reused it, in
                                                                                                                                   symbiosis with the environment.
                                                                                                                                       It is a cultural path that may seem twisted and uncertain, but its aim is to valorize
                                                                                                                                   the entire history of the territory, not only one historical period, even if it is believed to
                                                                                                                                   be the most important, as it is a valuable piece of evidence for civilization.
                                                                                                                                       A ready-made in reverse. In archeology a common artifact of everyday use is
                                                                                                                                   elevated to the status of cultural heritage and work of art when, over time, it is evi-
                                                                                                                                   dence of civilization. It is therefore “used” in a situation that is different from the
                                                                                                                                   original one.
                                                                                                                                       In this case, for example, an Etruscan tomb, having lost its original function of sep-
                                                                                                                                   ulcher, becomes a shelter, a stable, a warehouse, a garage, a dwelling (maybe recon-
                                                                                                                                   secrated with a simple cross engraved on the walls): thus, a work of art becomes a
                                                                                                                                   common banal object, with all due respect to Duchamp and his “Fountain”.
                                                                                                                                       One last (and in this case, final) way these environments were used was, unfortu-
                                                                                                                                   nately, as illegal dumping grounds. Indeed, one of the aims of this paper is to encour-
                                                                                                                                   age people to respect these spaces which are extremely rich in history and culture and
                                                                                                                                   to give them back the dignity they deserve.


                                                                                                                                      3. Origins of the architecture of subtraction

                                                                                                                                        We are used to thinking about architecture as something built that emerges, that
                                                                                                                                   stands between the ground and the sky. After all the term “architecture”, of Greek ori-
                                                                                                                                   gin, derives from the terms arché meaning “challenge”, “departure”, “origin”, “foundation”
                                                                                                                                   or “guide”, and técton, which recalls several meanings, among which are “to invent”,
                                                                                                                                   “to create”, “to shape”, “to build” (Giacomo Devoto, etymological dictionary).
                                                                                                                                        It is Herodotus who brings the two terms together for the first time (ἀρχιτέκτων, Sto-
                                                                                                                                   rie III, 60, 4), wanting to indicate the person whose responsibility it is to provide the ra-
                                                                                                                                   tional rules to regulate construction.
                                                                                                                                        Much more recently, in 2007, Renzo Piano defines architecture as: “The most an-
                                                                                                                                   cient profession on Earth, the art of building, but also the art of representing things”.
                                                                                                                                        Yet, as observed earlier, there exists an architecture that does not build but exca-
                                                                                                                                   vates, does not add one piece to another, but removes the “superfluous”.


                                                                                        320
Figure 1. Pietro Canonica, Case nel tufo, Vetralla (inv. C. 339). Reproduced with the kind permission
of the Museo Pietro Canonica, Rome.


    It is a hidden architecture that could even be called camouflage, because it blends
into the landscape, and is literally “inside” it. But that does not make it any less spec-
tacular. It is an extremely ancient tradition that actually dates back to the stone age. It
is cave civilization: which in some cases is anything but primitive, with extremely re-




                                                                                                          CONSERVATION SCIENCE IN CULTURAL HERITAGE
fined creations, like the majestic facades of the temples excavated in the rock with
huge, decorated portals.
    The catacombs are another example: cemeteries excavated in the tuff composed of
subterranean passageways on different levels. Not places where people hid from perse-
cution – as tradition says – but a brilliant solution to optimize the little land available: a
kind of upside-down building [9]. Inside the catacombs several different kinds of architec-
ture can be seen, from arcosolia to real small temples, everything hewn from the rock.
    It is relatively recently that the attention of the scientific world has focused on the
diffusion and articulation of this architecture, obtained by carving material out of the
rock walls found in geological areas characterized by the sedimentation of materials
that are easy to work with using simple tools.
    In general, it is difficult to establish when rupestrian environments were excavat-
ed, due to the fact they are structures obtained through removing material and not
accumulating it, a circumstance that prevents the formation of stratigraphic deposits.
At times, when there is no indication of a relationship between the masonry struc-
tures or useful data that can be obtained from documentary sources or paintings in
the cavities themselves, it is impossible: therefore a way to try to date these environ-
ments has to be found, which means defining the various typologies in order to clas-
sify the cavities with distinctive recurrent elements, a methodology that has been ad-
opted for some years in the study of man-made cavities which has given important
results. [10]


                                                                                                        321
                                                                                                                                         Then there are towns of which there are two versions: like the village of Camerano,
                                                                                                                                   in the Regional Park of Mount Conero, in Marche. Below the level of the street is an-
                                                                                                                                   other proper village inside the village, carved into the sandstone rock. The numerous
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   underground tunnels running beneath the historical centre in a labyrinthine pattern, re-
                                                                                                                                   veal the presence of architectural embellishments in almost every space, bas-reliefs
                                                                                                                                   and decorations with friezes, ornamental motifs and religious symbols. Their origin is
                                                                                                                                   still uncertain due to the lack of specific studies and historical documentation. Oral tra-
                                                                                                                                   dition, always to be taken into account, especially when sources are scarce, informs us
                                                                                                                                   that: “There is more of Camerano below ground than above”.
                                                                                                                                         One fundamental function of an underground city is undoubtedly, protection: the un-
                                                                                                                                   derground tunnels allowed the population to hide in case of sieges or threats. And not
                                                                                                                                   only in ancient times; in 1944, during the wartime bombing, the whole hypogeal system
                                                                                                                                   was used as a shelter by the population, who spent twenty days inside the caves.
                                                                                                                                         Other examples of underground cities, a mirrored reflection of the city on the sur-
                                                                                                                                   face, can be found throughout Tuscia, from Viterbo to Orte and Vetralla (although their
                                                                                                                                   history and function have been forgotten) to nearby Orvieto and Narni.


                                                                                                                                      4. Characteristics of the architecture of subtraction

                                                                                                                                       There are multiple factors that motivated the necessity to carve dwellings from
                                                                                                                                   rocks and in general, depend on geographical location, climatic and environmental
                                                                                                                                   variability and available resources. [11]
                                                                                                                                       Apart from the origins that led to the creation and utilization of these underground
                                                                                                                                   cavities as shelters in adverse environmental contexts, what is more interesting to note
                                                                                                                                   is the variant that arises as a consequence of the geological structure of the terrain
                                                                                                                                   with its favourable conditions. These particular conditions derived from the fact that the
                                                                                                                                   soft rock was easy to work with, so it is easy to understand how the architecture of sub-
                                                                                                                                   traction provided a “building” solution that was immediate, logical and cheap.
                                                                                                                                       Excavating in such situations is more economical than building. Obviously, strictly
                                                                                                                                   from the point of view of the microclimate, a hollowed-out environment provides satis-
                                                                                                                                   factory conditions, because the temperature inside is stabilized, thus attenuating any
                                                                                                                                   daily or seasonal variations. This characteristic makes this type of environment ideal
                                                                                                                                   for use as cellars and storage spaces.
                                                                                                                                       Frequently however, the presence of only one opening onto the outside (as well as
                                                                                                                                   providing access to the environment) makes it a habitat that is dark and poorly venti-
                                                                                                                                   lated, and so is unhealthy and uninviting as a human dwelling.
                                                                                                                                       Excavating is the most accessible technique when resources and technologies are
                                                                                                                                   limited or underdeveloped. The rock is self-supporting and requires no additional
                                                                                                                                   equipment, other than a few simple tools for excavating and human strength.
                                                                                                                                       Despite the simplicity of the architectural techniques, underground architecture is
                                                                                                                                   extremely flexible due to the possibility of modelling the space according to one’s
                                                                                                                                   needs and personalizing it by enlarging existing spaces or adding recesses or rooms
                                                                                                                                   when needed. Another factor that may determine choosing structures excavated in the
                                                                                                                                   ground rather than constructing on the surface is that it provides the possibility of fully
                                                                                                                                   blending into the landscape and being visible only at close quarters. An essential char-
                                                                                                                                   acteristic not only for shelters but also for hermitages.
                                                                                                                                       It is also probable that people have gradually learned and acquired some forms of
                                                                                                                                   behavior by observing the animal world and the way in which they have been able to
                                                                                                                                   adapt to climatic environmental contexts.


                                                                                              322
   Below is a brief classification of the different varieties of architecture of subtraction
and an indication of some of the criteria that were applied:
   • Hypogeal structures are structures created by starting from the natural ground
       level and excavating downwards, in depth.
   • Rupestrian structures are structures where all the levels excavated in the rocks
       are above natural ground level.
   • Carved structures are those where subtraction involves not only the interior but
       also the exterior and models the shape of the traditional elevated built architec-
       ture (reproducing the structural models, the spatial organization, the friezes, the
       decorations). [11]
   •   Mixed structures are structures where the subterranean or rupestrian elements
       coexist with artificial parts built on the surface by extending the cavities outwards
       towards the exterior. [12]
    How is it possible that in some areas this type of architecture developed and was
used more extensively than in others? One important reason is evidently the composi-
tion of the subsoil and the rocks. The rocks must possess particular characteristics of
resistance and workability, which are typical characteristics of magmatic rocks. In Tus-
cia, the two most common types are tuff and peperino.
    The tuff (in latin: Tofus or Tophus), of different colours, such as beige, yellow, grey,
or dark brown, abundant in the volcanic districts of Latium, is a fairly resistant rock but
light and workable.
    The peperino or peperine, grey in color and speckled with black-coloured particles
similar to pepper grains (hence the name), is typical of the areas of Vitorchiano and So-
riano in Cimino, even though it is found in various areas of central Italy. The peperino
is also known as lapis ciminus, since it comes from the solidified lava of the Cimino vol-
cano in Tuscia, which is today inactive and called “Mount Cimino”. Peperino stone is
very resistant despite its being easily workable.




                                                                                                 CONSERVATION SCIENCE IN CULTURAL HERITAGE
    The architecture of subtraction is particularly interesting because, it has survived to
the present day almost uninterruptedly with the recovery of ancient structures convert-
ed into garages and cellars, and the excavation of new structures with the same func-
tion, particularly in the countryside. [13]


   5. Excavation techniques

    As pointed out, excavation techniques have remained the same over the centuries,
and are evident in the traces left behind on the rocks by the tools utilized over several
centuries. Therefore, to understand how these ancient structures were made, a full-
scale investigation into “present-day” ones was set up by interviewing some of the lo-
cal people who are still able to excavate these cavities in the rock and were able to de-
scribe the phases of the procedure. [14] The study provides a wealth of knowledge on
current excavation methods and the equipment that is used, facts that were also con-
firmed in the interviews I had with people who had either done the excavating or had
been present when the grottos or the cellars were being excavated.
    “After choosing a rocky wall that suits your needs as regards size and position
(usually oriented towards the south), the first thing you do is to make a rough outline of
the entrance to the space with the tip of your pick, based on the function of the space
and the needs of the occupants.


                                                                                               323
                                                                                                                                         You then gradually proceed with your pick to break the rock in the lower half of the
                                                                                                                                   drawing, inside the outline you have made for the opening, to reach a depth of approxi-
                                                                                                                                   mately 50 cm, at the same time the lines of the opening are made deeper with a pick, un-
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   til they form a groove, called in Italian cavarella (which recalls the vie cave mentioned
                                                                                                                                   earlier); this results in the upper half jutting forward and is separated from the rock face
                                                                                                                                   by about 10-15 cm. Later on, this part is detached from the rock by inserting wedges and
                                                                                                                                   shims into the groove, usually one wedge with another two, one on either side. In the
                                                                                                                                   past, the wedges were made of wood, today they are made of steel. In this first phase,
                                                                                                                                   the mass of rock that has been detached from the top part using the wedges must always
                                                                                                                                   be greater than the lower half cut away with the pick: in this way the stoneworker can
                                                                                                                                   stand on the step that has been created without using any scaffolding”. [14]
                                                                                                                                         For reasons of economy, the use of metal or wood scaffolding is almost always avoid-
                                                                                                                                   ed: the use of wood or the renting of scaffolding entails an expense that, even though
                                                                                                                                   minimal, is at odds with the nature of the rock excavation itself, which comes from the
                                                                                                                                   need to create a space which provides cover and shelter at no cost whatsoever.
                                                                                                                                         The process of excavating continues on the inside by removing the upper mass with
                                                                                                                                   the help of wedges. The last part to be removed is the bottom part that acts as a step.
                                                                                                                                         The stoneworker then proceeds to fix the surfaces of the interior with the tip of a
                                                                                                                                   pick: in fact the wedges are used to remove a sizable mass of rock from the wall, and
                                                                                                                                   thus make the job easier; however, their use does not produce smooth surfaces. As re-
                                                                                                                                   gards the ceiling and the upper part of the walls, if the size of the space is such that it
                                                                                                                                   exceeds the height of a person, the finishing is done during the removal of the rock, in
                                                                                                                                   other words while the rock step is still in place as it allows the ceiling to be reached.
                                                                                                                                         The floor, instead, can be fixed after the excavation. The practice of lowering the
                                                                                                                                   level of the floor using only a pick and creating one or two entrance steps is not very
                                                                                                                                   widespread, due to how these spaces are used (as garages for cars in residential ar-
                                                                                                                                   eas, for agricultural machinery in the countryside and, until a few decades ago, as a
                                                                                                                                   shelter for animals) and the need to avoid flooding in case of rain.
                                                                                                                                         Inside the excavated spaces essential recesses were likewise created in the rock:
                                                                                                                                   feeding troughs in the grottos which were used as stables and steps, or even stairs to
                                                                                                                                   connect the various spaces, other than the one that gave onto the road (usually cellars).
                                                                                                                                         Each local dialect has developed its own terminology for describing the environ-
                                                                                                                                   ments excavated in the rock, the construction technique, and the tools that were used.
                                                                                                                                   In the province of Viterbo the typically characteristic terms included in this study and
                                                                                                                                   personally encountered in the interviews, have all been handed down.
                                                                                                                                      • Affaccio: the entrance to the excavated space exclusively at the moment it is
                                                                                                                                          “drawn” on the rock wall.
                                                                                                                                      • Porta: the entrance after the environment has been excavated.
                                                                                                                                      • Cavarella: the v-shaped groove made with the pick into which the wedges are
                                                                                                                                          inserted.
                                                                                                                                      •   Zeppe: wedges made of wood or metal.
                                                                                                                                      •   Cielo: the ceiling of the environment.
                                                                                                                                      •   Cantoni: the upper corners of the entrance (affaccio) and of the environment.
                                                                                                                                      •   Cavare: excavate a hollow space in the rock.
                                                                                                                                      •   Polsetto: way in which the pick is held (cavare a polsetto).
                                                                                                                                      •   Da capo: from the top.
                                                                                                                                      •   Da piedi: from the bottom.


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    The essential tools include:
    • A double-pointed pick (piccone a due punte), also called a stoneworker’s pick
         (piccone da cavatore), it is typically used for cutting rock; this tool is also used
         in the first phase to define the entrance, and successively to do the final finish-
         ing. Very similar to the common pickaxe, it is smaller in size and has the pecu-
         liar characteristic of not having the usual flat blade but two pointed ends, due to
         the elementary need of having to deal with the problem of a broken tip in the
         quickest and most practical way; the handle is also smaller in size than a com-
         mon pick so it can be used in low narrow spaces.
    • Sledgehammer (mazza), a big hammer of about 2 kg. The handle varies in size
         and length; a short handle is used to break the rock on the inside and in the up-
         per part of the chamber, due to the limited space that would hinder any move-
         ment if an unwieldy tool were used; a long handle is used to break the rock in
         the lower part of the excavated chamber or outside it, since this type of imple-
         ment increases the force that is exerted.
    • Wedges and shims (cunei e zeppe) are pieces of hard wood or, today, also
         made of metal, with a V-shaped longitudinal section which, when inserted into
         crevices in the rock (cavarelle), allow huge blocks of stone to become detached
         with the minimum of effort. In particular, the wood wedge is hammered into the
         crevices and then wetted, so it dilates, making it easy to detach the pieces of
         stone. On the other hand, metal wedges are used with thin strips, also made of
         metal, that are wider than the wedge itself and positioned between the wedge
         and the rock thus preventing the wedge from breaking the inner sides of the
         crevice and evenly distributing the applied force along the rock face. The wedg-
         es are then sledgehammered until the piece becomes detached.
    It would be extremely interesting to study the traces left by these tools to compare
them with traces found in other excavated environments.
    The traces left on the walls by the pick are clearly visible and can be found on the




                                                                                                       CONSERVATION SCIENCE IN CULTURAL HERITAGE
walls, the floor and the ceiling. These marks are grooves ranging from 10-20 cm in length,
and are 1-4 cm deep, and are slightly curvilinear on the flat surfaces. In the upper corners
inside the chamber, both towards the entrance and towards the back wall, they are in-
stead strongly curvilinear: since the upper corners are where the walls meet the ceiling
and the floor, they need a more accurate finishing with higher definition. These grooves
show that the pick was held sideways at an angle of 45° when used. Instead, when the
pick is used frontally, to finish the interior of recesses or troughs, or the inferior part of the
walls, it leaves shorter grooves that are less deep, and end with a little circular mark.
    The traces left by the wedges are usually visible only outside the excavated envi-
ronment, since the interior finishing, carried out with the pick, has erased them. They
are small, rectangular, square or circular shaped holes, that are always irregular and
have fracture marks around them.
    In conclusion, the traces left by the tools confirm how the simple cheap excavation
technique that was used, needed very few essential tools and has remained almost
unchanged over the centuries [14].


    6. The types of architecture of subtraction

   The following is a list of the different types of architecture of subtraction with re-
spective images.


                                                                                                     325
                                                                                                                                   Types

                                                                                                                                   1.   Apiaries (Figure 2)
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   2.   Canals (Figure 3) and tunnels
                                                                                                                                   3.   Cellars (Figure 4)
                                                                                                                                   4.   Hypogeal houses (Figure 5-6)
                                                                                                                                   5.   Caves and mines (Figure 7)
                                                                                                                                   6.   Cisterns, semi-subterranean or underground structures used to store snow
                                                                                                                                        (conserve della neve) and ice-houses (Figure 8)
                                                                                                                                   7.   Dovecotes (Figure 9)
                                                                                                                                   8.   Furnaces (Figure 10)
                                                                                                                                   9.   Hen houses (Figure 11)
                                                                                                                                   10. Artisan workshops
                                                                                                                                   11. Storage spaces and agricultural shelters (Figure 12)
                                                                                                                                   12. Pigsties (Figure 13)
                                                                                                                                   13. Wells
                                                                                                                                   14. Refuges (Figure 14)
                                                                                                                                   15. Sanctuaries and hermitages (Figure 15)
                                                                                                                                   16. Stables (Figure 16)
                                                                                                                                   17. Reused tombs
                                                                                                                                   18. Retention basins (Troscioni) (Figure 17)
                                                                                                                                   19. Basins (Figure 18-19)
                                                                                                                                   20. Vie Cave (Figure 20) and ditches.




                                                                                                                                               Figure 2. Apiary, Soriano (VT). Photo Alessandra Castagnolo.


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                          Figure 3.
                          Canal, Strada Vetrallese, km.3.
                          Vetralla (VT).
                          Photo Andrea Natali.




Figure 4.
Cellar,
Vetralla (VT).
Photo Gabriella Decini.




Figure 5.                                                     CONSERVATION SCIENCE IN CULTURAL HERITAGE
Hypogeal house,
Vallerano (VT).
Photo Gabriella Decini.




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                                                                                                                                                                       Figure. 6.
                                                                                                                                                                       Hypogeal house,
                                                                                                                                                                       Corviano, Soriano (VT).
                                                                                                                                                                       Photo Fabrizio Allegrini.
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   Figure 7.
                                                                                                                                   Holy area of Fosso Bicione,
                                                                                                                                   Monterano, Rome.
                                                                                                                                   Used as a mine until 1900.
                                                                                                                                   Photo Gabriella Decini.




                                                                                                                                                                 Figure 8.
                                                                                                                                                                 Ice-house in the wood of Sasseto,
                                                                                                                                                                 Torre Alfina (VT).
                                                                                                                                                                 Photo Elena Ronca.




                                                                                           328
                            Figure 9.
                            Dovecote, Blera (VT).
                            Photo Andrea Natali.




Figure 10.
Furnace and
workshop for the
production of terracotta,
Via dei Pilari,
Vetralla (VT).
Photo Andrea Natali.




                                                                             CONSERVATION SCIENCE IN CULTURAL HERITAGE
                                                    Figure 11.
                                                    Henhouse,
                                                    Vetralla (VT).
                                                    Photo Andrea Natali.




                                                                           329
                                                                                                                                                             Figure 12.
                                                                                                                                                             Agricultural shelter,
                                                                                                                                                             Vetralla (VT).
                                                                                                                                                             Photo Gabriella Decini.
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   Figure 13.
                                                                                                                                   Pigsty,
                                                                                                                                   Castel Di Salce (VT).
                                                                                                                                   Photo Gabriella Decini.




                                                                                                                                                             Figure 14.
                                                                                                                                                             Air-raid shelter,
                                                                                                                                                             Palazzo Di Vico, Viter-
                                                                                                                                                             bo.
                                                                                                                                                             Photo Gabriella Decini.




                                                                                           330
Figure 15.
Hermitage of San Girolamo,
woods of Monte Fogliano,
Vetralla (VT).
Photo Andrea Natali.




                             Figure 16.
                             Stable,
                             Vetralla (VT).
                             Photo Andrea Natali.




                                                      CONSERVATION SCIENCE IN CULTURAL HERITAGE




Figure 17.
Troscione del Confine,
Bosco di Monte Fogliano,
Vetralla (VT).
Foto Andrea Natali.




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                                                                                                                                                                  Figure 18.
                                                                                                                                                                  Basin for
                                                                                                                                                                  agricultural work.
                                                                                                                                                                  Bomarzo (VT).
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                                                  Photo Gabriella Decini.




                                                                                                                                   Figure 19.
                                                                                                                                   Thermal basin dell’Asinello,
                                                                                                                                   Castel D’Asso, Viterbo.
                                                                                                                                   Photo Andrea Natali.




                                                                                                                                                                     Figure 20.
                                                                                                                                                                     Via Cava,
                                                                                                                                                                     Pitigliano (GR).
                                                                                                                                                                     Photo Aldo Paolelli.




                                                                                                332
   7. Project for the conservation and valorization of the architecture of
      subtraction inserted in the rural landscape of Central Italy

     Once attention has been called to this type of architecture and the economic impor-
tance it had for rural society has been highlighted, as well as the cultural relevance it
still has today, a project should be drafted for the conservation and valorization of the
architecture of subtraction that exists in the rural landscape of Central Italy, with the in-
volvement of the local communities and administrations, an essential aspect if the proj-
ect is to be successful.
     A location in Vetralla (VT), on a road called strada Volparo, along the pilgrimage
route of the via Francigena, has been identified as a suitable site for valorization. The
Via Francigena is the route that starts from Canterbury in South England and travels
through France and Switzerland to Rome. It was once the destination of pilgrims and
crusaders and is today an important religious and cultural itinerary in Europe, covered
every year by 35000 people (2018 data).
     Just outside the twelfth and fourteenth century city walls of Vetralla [15] there is an
excavated road where there are numerous excavated grottos, in a state of abandon
and degradation, which are used for illegal dumping.
     The project, presented to the Municipality of Vetralla (registered under protocol
n. 0024525 of 23/08/2021), provides for the cleaning and reclamation of the sites and
inside the spaces, the subsequent installation of an open-air museum displaying its ru-
ral cultural history with correctly illuminated and securely installed exhibits, that recall
age-old crafts, such as breeding, transportation using carts drawn by animals, and ar-
tisans and farmers with tools relating to the rural life of the nineteenth and twentieth
centuries, together with information systems and parking areas for tourists that pass
along the road.
     The open-air museum will enable visitors to learn about this particular architectur-
al style, help to restore a road in a state of abandonment, and improve the image of the




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
territory, in addition to raising awareness about its history, culture, traditions and local
products. [16-21]

                                                                         Figure 21.
                                                                         Grotto used as a
                                                                         dumping site,
                                                                         Strada Volparo on
                                                                         Via Francigena,
                                                                         Vetralla (VT).
                                                                         Photo Andrea Natali.




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   Biographical notes

    Andrea Natali carries out research activity, didactics and consulting in the field of
Cultural Heritage Conservation.
    He graduated in “Conservation of Cultural Heritage” at the University of Tuscia and
has received two research grants at the University of Bologna. He holds a Master in
“Community narrators” DIBAF, University of Tuscia (Viterbo, Italy).
    He has carried out scientific research at the Department of Cultural Heritage and
the Department of Architecture and Territorial Planning at the University of Bologna,
the Institute for Conservation and Valorization of the National Research Council (CNR).
    He has carried out didactic work and continues to do so in University, Academy and
Master courses in sectors related to the field of conservation, restoration, art diagnos-
tics, artwork authentication, management and valorization of cultural and landscape
heritage, and planning and promotion of artistic and cultural events. He is the owner of
the company Andrea Natali “Cultural Heritage Conservation”. He is a mediator/moder-
ator. He is the Editorial Secretary of the Journal “Conservation Science in Cultural Her-
itage” and a member of the Scientific Committee and works in the Scientific Coordina-
tion of the journal “Scienze e Ricerche”. He has been an Expert in the Chamber of
Arbitration for public contracts at the National Authority for Anti-corruption. He is the
author and coauthor of more than 60 publications in the sector of conservation and val-
orization of cultural heritage which include scientific monographs and treatises used as
university course textbooks. He has also been a speaker in more than 60 conventions
and conferences.

    Maria Letizia De Luca is an architect. She has been a member of the Order of Ar-




                                                                                               CONSERVATION SCIENCE IN CULTURAL HERITAGE
chitects and Landscape Architects of Rome and the Province since 1995 (No.11038).
She has collaborated with major architectural firms and has carried out general design
activities, the development of executive design and has been responsible for the graph-
ic elaboration of projects, and the development of architectural and constructive details
for private commissions, including the prestigious Bulgari boutiques in Italy, Europe
and America. Since 1995, she has worked in her professional studio in Castelnuovo di
Porto (Rome, Italy), with a particular focus on building design, interior architecture and
renovation, in historic centers. She performs technical appraisals for individuals and for
the court of Tivoli as a court-appointed technical consultant.


   Summary

     The architecture of subtraction in rural landscapes is a type of architecture which
was of great economic and cultural value for rural society until the twentieth century.
Knowledge, cataloguing, conservation and valorization of architecture have therefore
all become essential elements in protecting the culture and the rural landscape of Cen-
tral Italy. The article presents and catalogues this type of architecture and proposes a
project that aims at the recovery and valorization of several abandoned and degraded
excavated sites, to set up an open-air museum that focuses on the rural and artisan life
of the nineteenth and twentieth century.


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                                                                                                                                      Riassunto

                                                                                                                                       L’architettura della sottrazione inserita nel paesaggio rurale è una tipologia di
A. Natali, M.L. De Luca - The architecture of subtraction in the rural landscape of central Italy: conservation and valorization




                                                                                                                                   architettura che ha avuto, per la società rurale, una importante valenza economica e
                                                                                                                                   culturale fino al XX secolo. La conoscenza, la catalogazione, la conservazione e la va-
                                                                                                                                   lorizzazione dell’architettura della sottrazione diventano, quindi, fondamentali per pre-
                                                                                                                                   servare la cultura e il paesaggio rurale del centro Italia. L’articolo presenta e cataloga
                                                                                                                                   tale tipologia di architettura e propone un progetto, finalizzato al recupero e alla valoriz-
                                                                                                                                   zazione di alcuni siti scavati abbandonati e degradati, per la realizzazione di un Museo
                                                                                                                                   diffuso della civiltà contadina e artigiana dei secoli XIX e XX.




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