This is a souterrain, a type of stone-lined underground passage or chamber built during the early medieval period in Ireland, most commonly as storage space or a place of refuge. What makes this particular example quietly remarkable is that its wooden floor planks and a large central beam were still present when excavators finally reached them.

The structure was uncovered in 2000 during excavation led by Donald Murphy. The souterrain consists of a single rectangular chamber connected to a possible creep, a low narrow passage typically used to access a souterrain from ground level, leading off to the north-west. The chamber had not escaped entirely intact; the side-walls had been robbed of stone in recent years, and the roof had partially collapsed. But the wooden elements at the base of the chamber proved extraordinarily informative. A single large timber beam, likely a lintel, was submitted for radiocarbon dating, returning a date of AD 661 to 668. That places its construction firmly in the early medieval period, when ringforts, circular enclosures defined by earthen banks or stone walls, were a common form of rural settlement across Ireland. The souterrain sat at the centre of just such an enclosure, catalogued separately in the archaeological record.