The depression follows a rough T-shape, with a long axis of 8.3 metres running roughly north-north-west to south-south-east, and a shorter arm of 4 metres branching off near its south-eastern end. At up to 1.2 metres deep, and with large stones still visible along its sides, this is the collapsed or silted remains of a souterrain, an underground stone-lined passage or chamber typically built during the early medieval period, most likely between the seventh and twelfth centuries. Souterrains are found in their hundreds across Ireland, usually associated with ringforts, and are thought to have served as places of refuge, cool storage, or both.

This particular souterrain sits within the southern rath of a conjoined ringfort, meaning two circular enclosures linked together, a less common arrangement that suggests the site may have housed a household of some status or complexity. A fallen tree trunk now partly obscures the depression, and vegetation has done the rest, so the T-shaped plan that survives in the ground is more legible on paper than it is underfoot. The dimensions alone, nearly nine metres along the main axis, indicate a structure of considerable scale when it was in use.