Nothing about it announces itself. There are no exposed stones, no visible structural remains, yet the shape is too regular and too purposeful to be accidental.

The depression is thought to be the collapsed remnant of a souterrain, an underground passage or chamber, typically stone-lined and roofed with large slabs, which were commonly built in early medieval Ireland as places of refuge, cool storage, or concealment. When such a structure falls in on itself over centuries, the roof stones sink and the earth settles into exactly this kind of long, shallow trough. The cashel it sits within, a cashel being a roughly circular stone-walled enclosure associated with early medieval settlement, is recorded separately, and the souterrain appears to have run from near the northern wall inward toward the heart of the enclosed space, which is a fairly typical arrangement for such features.