Beneath or beside what may once have been a cashel, a type of early medieval stone-walled enclosure typically associated with a farmstead or small settlement, there lies a souterrain that has left no visible trace on the surface whatsoever. The structure is entirely underground, entirely ruined, and entirely invisible to anyone walking the land above it.

A souterrain is a man-made underground passage or chamber, usually dry-built from stone, and associated in Ireland with early medieval settlement. They served various purposes, most likely food storage, refuge, or both, and are found across the country in their hundreds. This one was recorded by Redington in 1912, who noted that local people referred to it not as a souterrain but as an "uan", a vernacular term that suggests the feature had its own distinct place in local knowledge even then. Redington described a main chamber roughly 3.9 metres long and 1.2 metres wide, narrowing at its western end into a passage only 0.6 metres across and about 1.8 metres in length. That constriction, a squeeze-point at the entrance to a tighter inner section, is fairly characteristic of the type, and may have served a defensive function, making it difficult for an unwelcome visitor to pass through quickly. By the time Redington wrote his description, the structure was already much ruined, and no surface trace has been recorded since.