 They were built on the left bank of the Poddle close to its confluence with the Liffey.At a later date – possibly in the 9th century – these sunken structures were filled in and replaced with more densely spaced post-and-wattle structures indicative of more intensive settlement.These later dwellings are now identified as Type I houses, characterised by the possession of a central hearth flanked by two raised benches or bedding areas, a roof supported by four internal posts, and a doorway at each end of the building.