They consist of accumulated heaps of fire-cracked stone and dark, charcoal-rich soil, the debris of a process in which stones were heated and then plunged into water-filled troughs to bring the water to a boil. What the boiling water was actually used for, whether cooking, bathing, hide-working, or something else entirely, remains a matter of genuine debate among archaeologists. The example at Mitchellsfort, near Glanmire in County Cork, came to light not through any planned investigation but because a road was being built over it.

Construction work for the N8 Glanmire-Watergrasshill Bypass disturbed the site, prompting an excavation in 2001. What archaeologists uncovered was a spread of heat-shattered stones and charcoal-enriched soil measuring roughly eleven metres east to west and four metres north to south, surviving to a depth of about twenty-five centimetres. The material had already been cut through by earlier drainage works, so the assemblage was fragmentary by the time it was properly examined. Crucially, no trough or hearth survived, meaning the functional core of the site, the pit or wooden vessel that would have held the water, and the fire that heated the stones, had been lost before anyone had a chance to record it. What remained was essentially the cold waste heap, the discarded stones cracked by thermal shock, piled up over repeated use across what may have been centuries.