They appear as low, horseshoe-shaped mounds, typically dark with charred and cracked stone, sitting close to a stream or boggy ground. The one recorded at Newtown in County Kilkenny is one such site, quietly occupying its place in the landscape as it has done for several millennia.

The term fulacht fia, sometimes rendered as fulacht fiadh, refers to these ancient burnt mound sites, the majority of which date to the Bronze Age, roughly 1500 to 500 BC, though some are older or later. The standard interpretation is that they functioned as cooking sites. A timber-lined trough would be dug into the ground near a water source, filled with water, and then heated by dropping fire-cracked stones into it until the water boiled. Repeated heating and rapid cooling causes stone to fracture, and it is the accumulated debris of these shattered stones that forms the characteristic mound we see today. Some archaeologists have proposed additional uses, including textile processing, leather working, or bathing, and the debate has never been fully settled. What is consistent across Ireland is the pattern: water nearby, burnt stone, a hollow or trough at the centre, and a mound built up over many episodes of use.