Heritage of Mercury. Almadén and Idrija

Heritage of Mercury. Almadén and Idrija

The property includes the mining sites of Almadén (Spain), where mercury (quicksilver) has been extracted since antiquity, and Idrija (Slovenia), where mercury was first found in AD1490. The Spanish property includes buildings relating to its mining history, including Retamar Castle, religious buildings and traditional dwellings. The site in Idrija notably features mercury stores and infrastructure, as well as miners’ living quarters, and a miners’ theatre. The sites bear testimony to the intercontinental trade in mercury which generated important exchanges between Europe and America over the centuries. Together they represent the two largest mercury mines in the world, operational until recent times.

Patrimoine du mercure. Almadén et Idrija

Le bien inclut les sites miniers d'Almadén (Espagne), où le mercure (vif-argent) a été extrait depuis l'Antiquité, et d’Idrija (Slovénie), où du mercure a été trouvé pour la première fois en 1490 après J.-C. La partie espagnole du bien comprend des bâtiments liés à l'histoire minière du site, notamment le château Retamar, des édifices religieux et des puits traditionnels. Le site d'Idrija présente notamment des entrepôts de mercure et des infrastructures, ainsi que des cités de mineurs et un théâtre des mineurs. Le site témoigne du commerce intercontinental du mercure qui a généré d'importants échanges entre l'Europe et l'Amérique pendant des siècles. Les deux sites sont les deux plus grandes mines de mercure au monde et sont restés en fonctionnement jusqu'à une période récente.

Patrimonio del mercurio (Almadén e Idria)

El sitio comprende las minas de Almadén, en España, donde se ha extraído mercurio (azogue) desde la antigüedad y las de Idria, en Eslovenia, donde se halló mercurio por primera vez en el año 1490. El sitio español incluye varios lugares relacionados con su historia minera, como el castillo de Retamar, edificios religiosos y pozos tradicionales. En Idria hay almacenes e infraestructura relacionada con el mercurio, así como viviendas de mineros y un teatro. Ambos sitios dan testimonio del comercio intercontinental del mercurio, que generó importantes intercambios entre Europa y América durante siglos. Las de Almadén e Idria son las minas de mercurio más grandes del mundo y estuvieron operativas hasta hace pocos años.

source: UNESCO/ERI

Erfgoed van kwik in Almadén en Idrija

Dit erfgoed bestaat uit de Spaanse mijn van Almadén, waar kwik werd gewonnen sinds de oudheid en de Sloveense mijn van Idrija, waar in 1490 na Christus voor het eerst kwik werd gevonden. Het Spaanse gebied heeft bouwwerken die te maken hebben met de mijnbouwgeschiedenis, waaronder het kasteel Retamar, religieuze gebouwen en traditionele woningen. De omgeving in Idrija kent vooral opslagplaatsen voor kwikzilver en de daaraan gerelateerde infrastructuur, maar ook woningen en een theater voor de mijnwerkers. De plekken getuigen van de intercontinentale kwikhandel, die belangrijke uitwisselingen tussen Europa en Amerika genereerde. Samen vertegenwoordigen ze de twee grootste kwikmijnen ter wereld, tot voor kort nog operationeel.

Source: unesco.nl

  • English
  • French
  • Spanish
  • Dutch
Puerta de Carlos IV © Joaquín García Rayo
Outstanding Universal Value

Brief synthesis

Mercury is a relatively rare metal, whose use has long been irreplaceable in a variety of technical, chemical and industrial processes. It has only been produced in substantial quantities and over a long period by a small number of mines worldwide, of which the two largest, until recent times, were at Almadén in Spain and Idrija in Slovenia. These two mining towns, whose origins date from ancient or Medieval times, demonstrate the lengthy period over which a socio-technical system of extraction specific to this metal was in operation, and the process of evolution it underwent. Controlling mercury extraction enabled control of the market, which very quickly became intercontinental in scope because of its decisive role in the extraction of silver from deposits in the New World. A heavy metal, which is liquid at room temperature and has very specific chemical and physical properties, mercury is also a pollutant, which is dangerous for human health. The two sites contain technical remains of large numbers of mine shafts, and their galleries and surface facilities, with artefacts which are specific to the extraction of mercury-bearing ores; they also include significant urban, monumental and infrastructure elements and material and symbolic materials associated with the life styles and social organisation of mercury extraction.

Criterion (ii) : Mercury extraction took place in a very limited number of mines, of which the two largest were Almadén and Idrija. From the Renaissance period in Europe, the activity took on an international dimension. Its worldwide strategic importance increased steadily, particularly because of its role in the working of gold and silver mines in America. The interchanges were at once economic, financial and related to technical expertise.

Criterion (iv) : The mining sites of Almadén and Idrija constitute the most important heritage left behind by the intensive extraction of mercury, particularly in the modern and contemporary periods. This dual testimony is unique, and it illustrates the various industrial, territorial, urban and social elements of a specific sociotechnical system in the mining and metal production industries.


The mining sites of Almadén and Idrija form a coherent whole with complementary components, satisfactorily illustrating all the technical, cultural and social aspects associated with mercury extraction. The elements are present in sufficient number to enable satisfactory interpretation. These are the two most significant sites for this activity to have been preserved, in terms of volumes produced, historical duration, and the completeness of the evidence provided. The integrity of the serial property has been justified.


At both sites, the presence of mining infrastructure elements both underground at on the surface, the presence of technical artefacts linked to mining extraction, its upstream needs (hydraulic energy, wood) and its conversion into “quicksilver” (furnaces), its transport and its storage are authentic. This also applies to the urban and monumental elements, and for the testimony to the miners’ working conditions.

Protection and management requirements

The protection measures for the sites are satisfactory; in both cases they have led to municipal general plans of land use and the control of construction works projects which could affect the sites. These urban and rural planning measures also apply to the buffer zones. At Almadén however, the existence of projects which could have a visual impact on the property and the belated inclusion of the property and its boundaries in the municipal general plan demonstrate the need for closer cooperation between the municipal authorities and the property management entity. For both sites, a satisfactory local management system exists, and the overarching International Committee for the coordination of the serial property has demonstrated that it functions satisfactorily.

Long Description

The sites forming part of the proposed series constitute the most noteworthy examples of mercury mines in the world and because of this they have had an important role in the history of humanity, from ancient times up to the present day. Their moment of greatest historical significance was at the point when they complemented each other to achieve the production that was sent to America along Intercontinental Camino Real of the Spanish Empire, from Europe to Spanish America.

It dates from the second half of the 16 th Century, when the mercury amalgamation process made possible the large-scale exploitation of the silver of New Spain. Europe and America were closely tied together in a structure linking ports and cities, peoples and communication nodes in order to ensure the stability of the economic model of trading monopolies and other cultural and spiritual values developed by the Spanish Monarchy to serve as the basis or the goal of the Empire.

The transcendence of this phenomenon was such that while it marked the territorial structure of America, among other aspects, it also influenced the subsequent development of the mercury culture on both sides of the Atlantic and has continued to the present day.

A relative rare metal, liquid at room temperature, mercury is produced only by a few mines across the world, of which the largest is at Almadén in Spain and the second largest at Idrija in Slovenia. In addition to the aforementioned historical link, there are many similarities between the two mining complexes in terms of other historical periods, the way in which the population responded to the difficult living conditions of mercury production, and especially the amazing technical and scientific response to all kinds of challenges. They jointly form a set of assets constituting a serial property representing a complex and inter complementary mercury mining engineering methods and related industrial and technical development from the Roman Empire time to the fi rst years of the 21th century.It  also offers a complete panorama of the different uses and utilities of mercury throughout history.