It is easy to miss and easier still to misread, but what remains here is a sweathouse, one of the more peculiar survivals of early Irish rural life. These structures, known in Irish as tigh alluis, functioned as a kind of indigenous sauna. A fire would be lit inside to heat the stone walls, the embers cleared away, and a person crawled in through a low doorway to sweat out illness or exhaustion. The practice was once widespread across Ulster and Connacht, and this example in Pollalaher belongs to that tradition.

The structure is built in drystone, meaning the walls are laid without mortar, relying entirely on the careful fitting of stone against stone. Its internal diameter measures one and a half metres, with a maximum surviving height of just under a metre. It was set into the hillside and originally opened to the west, though the doorway itself no longer survives, and the roof is gone entirely. The esker ridge on which it sits is a long gravel and sand formation deposited by glacial meltwater, a landscape feature common across the Irish midlands, and the choice of such elevated, well-drained ground for a structure like this was unlikely to be accidental.