One hollow measures roughly 3.6 metres east to west and 2.2 metres north to south, dropping about 1.5 metres below the surrounding surface. A second, rounder depression, about 2 metres across and a metre deep, sits a couple of metres to the west. Together, they are the surface signature of a souterrain, an underground stone-lined passage or chamber built during the early medieval period, most commonly between the sixth and twelfth centuries. Souterrains were typically associated with ringforts, the circular enclosed farmsteads that once defined the Irish rural landscape, and were used for storage, refuge, or both.

The ringfort here, recorded separately in the Cork archaeological record, would once have been an inhabited enclosure, its souterrain tucked beneath the interior where it could be accessed discreetly. The subsidence visible today is a familiar fate for these structures: as their corbelled stone roofs lose support over centuries, the ground above gradually slumps. What remains is essentially a negative space, a rough outline of chambers that no longer hold their shape, readable only as a subtle irregularity in the turf. Without excavation, the full extent of the underground complex at Lisbealad is unknown.