A souterrain is an underground stone-lined passage or chamber, typically constructed during the early medieval period in Ireland, often used for storage, shelter, or refuge. This one has vanished so completely from the surface that the only clue to its existence is a faint depression in the ground, noticed by observers nearly a century ago and not meaningfully added to since.

In 1934, a researcher named Bowman recorded a hollow on the north side of the interior of the ringfort, interpreting it as marking the position of a souterrain below. A ringfort, to give it its broadest description, is a roughly circular enclosure defined by an earthen bank and ditch, the standard form of a rural homestead across early medieval Ireland. Three years after Bowman's note, a second observer named Broker recorded the same site, confirming the depression was still discernible. That is, essentially, the full extent of the documented history. No excavation appears to have followed, and by the time later accounts were compiled, the site had no visible surface trace remaining at all. The souterrain's existence is inferred rather than confirmed, its location approximate, its contents entirely unknown.