The example at Cloonnagashel in County Mayo is one such site, a low crescent-shaped mound of fire-cracked stones and charred material that would be easy to walk past without a second thought. Known in Irish archaeology as fulachta fiadh, these features are typically found near water and are thought to date from the Bronze Age, roughly 1500 to 500 BC, though some span into the early medieval period. The standard interpretation holds that stones were heated in a fire, then dropped into a water-filled trough to bring it to the boil, leaving behind the characteristic mound of shattered, heat-stressed rock that accumulates over repeated use. What they were actually used for, whether cooking, bathing, textile processing, or something else entirely, remains a subject of genuine archaeological debate.

Cloonnagashel is a small townland in Mayo, and like many rural areas of the west of Ireland, the ground beneath and around it has never been fully excavated or systematically studied at a fine-grained level. The burnt mound here is recorded as a monument, catalogued among the many such features that dot this part of Connacht, where boggy, low-lying ground provided both the standing water and the fuel that these sites seem to have required. Without further excavated evidence specific to this site, the details of its date, scale, and use remain open questions.