The 1919 Ordnance Survey six-inch map labels the feature simply as 'Cave', which is the kind of cartographic shrug that tends to stick to things no one quite knows how to classify. What it actually marks is a souterrain, an artificially constructed underground passage or chamber, typically built during the early medieval period and associated with nearby ringforts, used variously for storage, refuge, or both.

The souterrain sits inside a rath, which is the Irish term for a ringfort, a circular enclosure defined by an earthen bank and interior scarp that once formed the boundary of a farmstead. At the south-eastern end of the surface depression, a horizontal stone lintel protrudes just above a small opening, 55 centimetres wide and 35 centimetres high, that leads into a drystone-built passage. Drystone construction means the walls are laid without mortar, the stones selected and stacked carefully enough to hold their own weight underground. The passage itself is roughly 75 centimetres wide and about 55 centimetres high, sloping downward and curving slightly to the south-east. A second opening, even smaller at 35 centimetres wide and 17 centimetres high, lies 7 metres to the south-east, set close against the enclosing scarp of the rath and still covered by its original lintel. Together, the two openings suggest the passage runs along a broadly north-west to south-east axis through the south-eastern quadrant of the enclosure, though the full extent of what lies between them underground remains a matter of inference from what is visible at the surface.