The only way in was from above, down through the roof, which makes it an unusual example of a souterrain, the underground stone-lined passages and chambers that early medieval Irish communities built beneath their settlements, most commonly for storage, refuge, or both.

The chamber itself is 4.4 metres long and 1.1 metres wide, a tight, deliberate space. Its walls are corbelled, meaning each course of stone projects slightly inward over the one below, a dry-stone technique that creates a self-supporting structure without mortar. The coursing is described as regular, suggesting careful construction rather than improvised work, and the end-walls curve slightly rather than meeting at sharp right angles. No roofing slabs survive, which is what leaves the entrance arrangement open to interpretation; without a roof, there is no visible hatch or shaft, only the inference that one existed. The chamber is recorded as part of a wider site at Cathair Na Gaoithe, with the surrounding bank forming the enclosure typical of a cashel, the Irish term for a stone-walled ringfort of the early medieval period.