At the centre of a ringfort, the circular earthwork enclosure that once served as a defended farmstead in early medieval Ireland, a broad L-shaped depression runs roughly twenty metres across the interior toward the southern scarp. It is about two and a half metres wide and drops around a metre below the surrounding surface. The leading interpretation is that this hollow marks the line of a collapsed souterrain, an underground passage or chamber built from stone and earth, typically used in early medieval Ireland for storage, refuge, or both.

Souterrains are found throughout Ireland, most commonly in association with ringforts, and the example at Davidstown appears to follow that pattern closely. The depression runs on a north-north-west to south-south-east axis before turning, tracing the characteristic bent or branching plan that many surviving souterrains share. Where intact souterrains were built to be concealed and load-bearing, a collapsed one leaves behind exactly this kind of elongated hollow as the roof structure fails and the ground above settles downward over time. The ringfort it sits within occupies a terrace position with open views to the south and west, a siting choice that would have made good practical sense to whoever farmed and fortified this spot in the early centuries of the first millennium.