These low, horseshoe-shaped mounds, typically found near water, are the remains of ancient cooking sites, or possibly bathing and brewing places, used predominantly during the Bronze Age. The mound itself is composed of fire-cracked stone, the accumulated debris of a surprisingly effective method: heating rocks in a fire and dropping them into a water-filled trough to bring it to the boil. The one at Knocknalappa, in County Clare, is a quiet example of this widespread but oddly anonymous class of monument, sitting in the landscape without the drama of a ringfort or the visibility of a standing stone.

Knocknalappa is a townland in Clare, and the presence of a fulacht fia there places it within a broader pattern of prehistoric activity across the county. Clare has a considerable concentration of these sites, many of them located close to streams, boggy ground, or natural springs, which would have provided the reliable water source the method requires. The cracked and reddened stone that forms the mound is essentially a byproduct, discarded after each use when the rocks, having fractured from repeated heating and sudden cooling, became too small to be practical. Over centuries, this waste material built up into the characteristic mound shape that survives today. Most fulachtaí fia in Ireland date to somewhere between 1500 and 500 BC, though the tradition may extend earlier in some areas.