The feature is a souterrain, a type of dry-stone tunnel constructed beneath or beside early medieval settlements, most likely for storage, refuge, or both. This one has fallen in on itself, leaving a stone-filled depression stretching more than 6.2 metres in length and roughly 1.2 metres wide, running in a northeast to southwest direction across the ground.

The souterrain sits within the northwest quadrant of a cashel, a term for a stone-walled enclosure, typically circular, that defined an early Irish farmstead or minor settlement. Where the passage meets its southwest end, it curves slightly southward before being blocked by stones and the roots and base of a tree, nature and collapse conspiring to seal it. At the northeast end, traces of the original side-walls still survive, offering a faint impression of the careful construction that once ran beneath. The structure was not simply dug but built, with upright stone walls and presumably a roofing arrangement of lintels or corbelled stone that has long since given way.