It is circular, barely a metre and a half across on the inside, built without mortar in the drystone tradition, and roofed with flat slabs in a beehive shape. The entrance on the western side is just forty centimetres high, which means that to get in, you would have to lie almost flat. This was, in its day, a sweathouse, the Irish equivalent of a sauna, where a fire would be lit inside, the chamber allowed to heat thoroughly, the embers raked out, and a person suffering from rheumatism or other ailments would crawl in and sweat for as long as they could bear it before plunging into a nearby stream or pool. It is a form of thermal therapy that was widely practised across Ireland well into the nineteenth century, and possibly much longer before that.

What makes this particular example quietly interesting is how thoroughly it escaped official notice. Neither the Ordnance Survey edition of 1836 nor the revised edition of 1876 recorded it, which suggests it was either overlooked by surveyors or simply not considered worth mapping, perhaps because such structures were then still common enough to seem unremarkable. By 1939, when Richardson examined and documented it, two of the flat closing slabs that formed the roof had already fallen. The beehive construction method, in which corbelled drystone courses are built inward and upward until the space can be capped, is an ancient technique found in Irish structures ranging from early monastic cells to field storage huts, and its use here on a remote Cavan hillside points to a vernacular building tradition that persisted largely outside the documentary record.