The label is accurate enough in spirit, though what survives today is less a cave than the ghost of one: a shallow, grassed-over depression in the ground, partly choked with boulders, tracing the outline of a structure that has long since fallen in on itself.

What the cartographers were recording was a souterrain, an underground passage or chamber built from stone, typically during the early medieval period in Ireland. Souterrains were constructed beneath or beside ringforts and were used variously for storage, refuge, or both; their cool, dark interiors suited the preservation of dairy produce and offered a concealed retreat in times of danger. This particular example sits in the south-eastern quadrant of a rath, which is the Irish term for a ringfort, a circular enclosure defined by an earthen bank and ditch. The souterrain lies adjacent to the inner face of that bank. The collapsed section that remains visible today measures around seven to eight metres along a north-west to south-east axis, and takes the form of two roughly square hollows, each approximately three to four metres across and no more than half a metre to seventy centimetres deep, joined by a shorter, narrower connecting section two metres across. The overall shape in plan suggests a simple two-chambered arrangement, which is a common enough configuration in Irish souterrains, though the full extent of the original structure is impossible to know from the surface alone.

What gives the site its quiet interest is precisely this layering of evidence: an early medieval underground structure, forgotten or at least unnamed by those who built it, identified on nineteenth-century maps under a plain English label, and now readable only as a pair of soft depressions in a Mayo field. The rath to which it belongs is still present, and the relationship between the two, the souterrain tucked against the inner bank, reflects the careful, practical thinking behind such constructions.