What they mark is a souterrain, an artificial tunnel of early medieval origin, typically built from drystone walling and roofed with flat stone lintels, used variously for storage, refuge, or concealment. Together, these three depressions trace a passage running northeast to southwest for at least twelve metres.

The entrance, at the northeastern end, sits roughly 0.6 metres below the present ground surface, its opening just 1.2 metres wide and 0.7 metres high. From there, the passage slopes gradually downward, widening slightly in height as it goes, with drystone-built side-walls carrying the stone lintels overhead. Six metres to the southwest, a second depression marks the point where some of those lintels have collapsed inward, leaving a visible sag in the earth. A third hollow at the far southwestern end indicates a further collapse, with a small damaged opening surviving, this one narrower still at 0.7 metres wide and only 0.5 metres high. The souterrain sits within what was once a defined ecclesiastical enclosure, suggesting it was constructed in association with an early religious settlement, a common enough arrangement in early medieval Ireland, where communities needed secure underground spaces close to where they lived and worked.