It is a souterrain, an ancient underground structure of the early medieval period, typically built or cut to serve as a place of refuge, cool storage, or concealment. This particular example is earth-cut rather than built up from stone, its single oval chamber measuring roughly four metres long, just under two metres wide, and not quite tall enough for most adults to stand upright in. Off the main chamber, annexes extend to the south and west, giving the structure a modest complexity that goes well beyond a simple pit or tunnel.

The construction shafts to the east still show four visible courses of stonework, suggesting that whoever dug and lined this chamber had some intention of permanence. What makes the site more intriguing still is a low earthen bank lying roughly ten metres to the west of the souterrain entrance. That bank is thought, on the basis of a personal communication from R. M. Cleary cited in the Cork archaeological record, to represent the remains of a ringfort, a type of enclosed farmstead common across early medieval Ireland, usually formed by one or more circular banks and ditches. The two features almost certainly belonged to the same settlement, with the souterrain functioning as an adjunct to whatever household once occupied the enclosure above. Excavation work noted in 2003 has shed some further light on the site, though the physical evidence that remains visible is modest.