Marked on the 1903 Ordnance Survey 6-inch map, this stone structure represents one of many such buildings that once dotted the Irish countryside, particularly in the northern and western counties. These small, corbelled chambers were Ireland's answer to the sauna; places where locals would gather to treat various ailments through the therapeutic use of heat and steam.

The sweathouse at Tullynavinn follows the typical construction pattern found throughout Donegal, built with dry stone walls that curve inward to form a beehive-shaped chamber. Users would light a turf fire inside to heat the stones, then remove the ashes before entering the intensely hot interior. Water thrown on the heated stones created steam, and bathers would remain inside for as long as they could tolerate the heat before plunging into a nearby stream or dousing themselves with cold water. This practice, which continued well into the 19th century in some areas, was believed to cure rheumatism, fevers, and various skin conditions.

While many sweathouses fell into disuse during the late 1800s as modern medical practices became more widespread, their presence on early Ordnance Survey maps helps archaeologists and historians locate and preserve these structures today. The Tullynavinn example, though now roofless and partially collapsed, remains an important piece of Ireland's medical heritage; a reminder of how communities once combined architecture, local knowledge, and natural resources to maintain their health long before the arrival of modern hospitals and clinics.