At Cloonnagleragh in County Mayo, one such site survives, a low horseshoe-shaped mound of burnt and shattered stone that would be easy to walk past without a second glance. Yet these modest earthworks represent a technology that was repeated, apparently deliberately, across millennia.

A fulacht fia, the term comes from Old Irish and is sometimes translated as "cooking place of the deer", typically consists of a trough dug into the ground near a water source, lined with timber or stone, and surrounded by a mound of fire-cracked rock. The standard interpretation is that stones were heated in a fire and then dropped into water in the trough, bringing it rapidly to a boil. Experiments have shown that a substantial quantity of water can be boiled this way in under thirty minutes, hot enough to cook meat. The cracked, heat-shattered stones were discarded after use, building up the characteristic mound over successive visits. Some researchers have proposed alternative uses, brewing, hide-working, bathing, though cooking remains the most widely accepted primary function. These sites cluster heavily in low-lying, boggy ground, which helps explain their survival; the waterlogged conditions that made them convenient to use also sealed and preserved them over the centuries. The example at Cloonnagleragh sits within this broader pattern of Bronze Age activity across the west of Ireland, a region where such monuments appear with particular frequency in the landscape.