It is, in fact, a sweathouse, one of Ireland's more peculiar vernacular structures, and the interior is considerably more deliberate than the rough exterior suggests. A corbelled roof, where flat stones are layered inward and upward to form a self-supporting dome without mortar, covers a chamber just over a metre and a half square and nearly two metres high. The entrance, set into the north face, is a tight lintelled opening barely half a metre wide and the same in height, meaning anyone entering would have had to crawl.

Sweathouses were used as a form of folk medicine, particularly from the medieval period onward, and possibly much earlier. A fire would be lit inside, the chamber heated thoroughly, and the ashes raked out before a person or small group entered to sweat out illness, joint pain, or fever, somewhat like a rudimentary sauna. This example at Killadiskert sits on the slope of a broad hill, roughly ten metres south of a route now known as the Miners Way, a green road that follows an old east-north-east to west-south-west alignment through this part of Leitrim. The structure appears on the 1907 edition of the six-inch Ordnance Survey map, with a house recorded about a hundred metres to the north, though the sweathouse itself is a considerably older type of monument than that mapping implies. The D-shaped mound enclosing it measures three metres east to west and two and a half metres north to south, rising between 0.8 and 2.2 metres depending on the angle of approach.

The Miners Way itself is worth noting as a locating detail. Walking this old track, the mound appears to the south of the road, unassuming enough that it could be passed without a second glance. The low entrance facing north would have made practical sense for a structure meant to retain heat, limiting the draw of cold air. What appears from a distance to be little more than a field mound resolves, on closer inspection, into something carefully and intentionally built.