They appear as low, horseshoe-shaped mounds, typically dark with charred and fire-cracked stone, sitting beside a natural water source. One such example lies at Ranaleen in County Kerry, a quiet presence in the landscape that most people would walk past without a second glance.

The term fulacht fia, sometimes translated loosely as "cooking place of the deer" or "wild place for cooking", refers to a type of ancient outdoor cooking site used predominantly during the Bronze Age, roughly between 1500 and 500 BC, though some examples date earlier or later. The standard interpretation is that a trough, cut into the ground and often lined with wood or stone, was filled with water and then heated by dropping fire-cracked stones into it. Those stones, once spent, were discarded to the side, building up the characteristic mound over generations of use. The method is surprisingly efficient; experiments have shown that a decent-sized trough can be brought to a boil within thirty minutes using this technique. Kerry has an exceptionally high concentration of these sites, partly because the wet, boggy ground has preserved both the mounds and the organic materials sometimes found within them.