A souterrain is an underground stone-lined passage or chamber, typically built during the early medieval period and associated with ringforts, the circular earthwork enclosures that served as farmsteads across early Christian Ireland. They were used variously for storage, refuge, or both. This one, though, has been sealed so long that it leaves no mark on the ground above it.

The record for this site traces back to a 1939 observation by Hartnett, who noted the souterrain lying inside the northern rampart of the ringfort, while also remarking that it had already been closed up by that point. The ringfort itself survives, but the underground structure beneath it is inaccessible and invisible, a chamber whose contents and condition remain entirely unknown.