The outline is roughly T-shaped, sunk no more than half a metre into the ground, its vegetation-covered length running nearly ten metres from west-northwest to east-southeast, with a smaller square recess branching off to the north near the southeastern end. Scattered along the sides and floor are several large flat stones, the remnants of a roofing system that once sealed the structure from above. What lies here is a souterrain, an artificially constructed underground passage or chamber built during the early medieval period, typically from around the sixth to the twelfth century.

Souterrains were a common feature of Irish ringforts, the circular enclosures of earth or stone within which farming families lived during the early medieval period. Their precise purpose remains a matter of some discussion among archaeologists, though storage and refuge are the most widely accepted explanations. Cool underground conditions would have suited the preservation of dairy produce, while the narrow, low passages would have made any armed pursuer deeply uncomfortable. This particular example sits in the west-northwest sector of a ringfort recorded in the county's archaeological inventory, its T-shaped plan suggesting a main passage with at least one subsidiary chamber, a more complex arrangement than the simplest single-chamber examples found elsewhere. The large lintel-like stones still visible at the surface would once have formed part of a corbelled or lintelled roof, the weight of the earth above holding everything in place.