A souterrain, which is an artificially constructed underground passage or chamber typically associated with early medieval settlement, lies collapsed within the northern half of a cashel, the type of dry-stone ringfort common across the west of Ireland. What remains is roughly six metres long on an east-west axis, and the sequence of spaces it describes tells you something about how deliberately it was designed.

The structure begins at the west as a rough stone passage, around three metres long and just over a metre wide, shallow enough now that it sits only half a metre below the present ground surface. Moving east, the passage narrows to about eighty centimetres, forming what is known as a creep, a deliberately tight constriction that would have slowed or deterred anyone trying to force their way through. Beyond that bottleneck, the passage opens into a chamber roughly two and a half metres across at its upper width. In the eastern half of this chamber, some of the original stonework survives in place, now thickly covered in moss. Souterrains of this kind are generally dated to the early medieval period and are thought to have served as refuges, storage spaces, or both, typically built in association with the ringforts or cashels above them. The narrowing creep is a recurring feature in Irish examples, and its presence here suggests a structure built with some care for the safety of whoever used it.