What was recorded as an elaborate souterrain, its roofing slabs collapsed across multiple chambers, now exists in a kind of archaeological limbo: documented, located, and yet practically invisible.

A souterrain is a man-made underground structure, typically built during the early medieval period in Ireland, consisting of one or more stone-lined passages or chambers dug into the earth and covered with large flat stones. They are found across the country, often in association with ringforts, the circular enclosed farmsteads that were the standard unit of rural settlement from roughly the sixth to the twelfth century. At Knockskagh, the souterrain sits within the southern portion of just such a ringfort, and the description of it as elaborate, with several distinct chambers, suggests it was a more ambitious construction than the simple single-passage type. The collapsed roofing is a common fate for these structures; once the capstones give way, the passages fill with rubble and soil, and the whole system becomes difficult to trace without excavation.