It is a sweathouse, a type of structure once used across rural Ireland as a form of therapeutic heat treatment, broadly comparable in function to a sauna. Fires would be lit inside to heat the stone walls, the embers cleared out, and a person would then squeeze through the low entrance and sit in the retained heat, sometimes emerging to plunge into a nearby stream. The presence of a natural spring and running water immediately beside this example suggests the site was chosen with exactly that sequence in mind.

The chamber is circular, built from stone with slightly inclined walls and a lintelled roof, meaning flat capstones laid horizontally across the top rather than a true arch. Its internal diameter is just one and a half metres, and it stands about one and eight tenths metres high, compact and deliberate in its construction. The entrance, facing south, is only fifty-five centimetres wide and sixty centimetres tall, requiring anyone entering to bend low. Roughly fifty metres to the south-east, the remains of a deserted farmstead suggest this was once part of a working upland landscape, the sweathouse serving a local community that has long since disappeared from the mountain. The structure appears on the 1914 edition of the Ordnance Survey six-inch map, though sweathouses as a tradition are considerably older than that record, with many examples across the north and west of Ireland understood to date from the eighteenth century or earlier.