Roughly two metres long, less than a metre wide, and less than a metre deep, it is partly lined with drystone walling, the kind of careful dry-laid stonework that suggests deliberate construction rather than natural collapse. Whether it was ever a souterrain, an underground passage or chamber typically built during the early medieval period as a place of refuge or storage, remains genuinely uncertain.

The site sits on an eastern platform of the hillside, about 350 metres east of the summit, at an exposed elevation of around 286 metres. Its position is striking in context: the Great Blasket is an island already defined by remoteness, and the upper reaches of Sliabh an Dúna are among its most windswept and least sheltered ground. Whoever shaped this hollow, and for whatever purpose, chose a location that offered little comfort. The description comes from J. Cuppage's 1986 archaeological survey of the Corca Dhuibhne region, the Dingle Peninsula, which catalogued numerous features across this coastline. Even within that survey, the classification of this particular feature was left open, noted as a possible souterrain rather than a confirmed one.