It looks, at first glance, like little more than a flat rock lying on the ground, but the opening it covers hints at something older and more deliberate underneath: a souterrain, the term for an artificial underground passage or chamber, typically constructed during the early medieval period in Ireland, probably as a place of refuge, storage, or concealment.

The slab, measuring approximately one metre by half a metre, may function as a lintel, the topmost stone spanning the entrance to a subterranean passage below. Its position within the ringfort places it in a context that would have been entirely familiar to early medieval communities across Ireland. Ringforts, which are enclosed farmsteads usually defined by one or more earthen banks and ditches, were commonly occupied between roughly the fifth and twelfth centuries, and souterrains are frequently found within them. Also recorded in the western half of the interior are three small circular depressions, each between twenty and thirty centimetres in diameter, whose relationship to the souterrain or to the broader site is not fully established. They may represent post-holes, erosion, or some other feature of the original occupation.