A sunken passage, visible for roughly two metres and just over a metre wide, cuts through the earth oriented roughly north-northeast to south-southwest, its eastern side still showing corbels, the protruding flat stones that would once have helped support a roof. By every outward sign, this looks like the entrance to a souterrain, an underground passage or chamber of the kind built throughout early medieval Ireland, typically used for food storage, refuge, or escape. Yet no chamber has been found. The passage leads nowhere detectable.

The feature sits in the north-western interior of the cashel, a type of early medieval ringfort built from dry-stone walling rather than earthen banks, positioned to the south of a built-up accumulation of cairn material. About two metres to the north of the sunken passage there is a crater-like depression in that cairn, roughly 1.4 metres in diameter, which might suggest a collapsed void beneath, though no confirmed underground space has been identified there either. Whether the souterrain was never completed, whether its chamber has simply collapsed beyond recognition, or whether what survives is a fragment of something more extensive that time and loose stone have obscured, the site does not readily give up an answer. The corbels on the eastern side remain the clearest evidence that this was, at minimum, a serious piece of construction rather than a natural feature or later disturbance.