The entrance has never been located. Cartographers mapping the area in 1897 labelled it simply "Cave" on the Ordnance Survey 25-inch plan, and the name carried into the 1920 edition of the six-inch map. That label is doing a lot of work. What lies beneath is considerably more deliberate than any natural hollow.

The structure is a souterrain, an artificially constructed underground passage typically associated with early medieval settlement in Ireland, used variously for storage, refuge, or as a cool larder. This one sits within the southern half of a cashel, a type of stone-walled enclosure common in early medieval Ireland, and its layout repays close attention. The main passage, largely running east to west, narrows to around a metre and a quarter in width in places, with a visible height of little more than a metre in the damaged central section, where roof lintels have fractured and fallen inward and a stretch of the north wall has given way. Further west, though, nine intact lintels survive, along with corbelled walling, a construction technique in which stones are stepped progressively inward to form a vault or support a roof. T. J. Westropp, writing in 1901, described a "cornice of long slabs projecting 12 inches or 13 inches over the edge" and noted what he called "ambrey-like recesses", small cupboard-like cavities cut into the wall, one of which measured roughly thirty centimetres square. A subsidiary passage branches off to the northeast and reaches a roughly circular underground space six metres in diameter filled with rubble, which may represent a beehive chamber whose corbelled roof has long since collapsed inward. The whole structure stretches 20.6 metres in total length, and its eastern end, though roofed with lintels, remains inaccessible.