They appear as low, horseshoe-shaped mounds, typically dark with charred and heat-shattered stone, and they cluster near water with a consistency that speaks to deliberate, repeated use. The one recorded at Killeens in County Cork is a local example of this extraordinarily widespread monument type, a feature that would have been entirely unremarkable to a Bronze Age community and is now, several millennia later, only partially understood.

The prevailing interpretation is that fulachtaí fia were outdoor cooking sites. The typical method involved heating stones in a fire, then dropping them into a water-filled trough to bring it to a boil, used for cooking meat. The mound itself is the accumulated debris of that process, cracked and discarded stones building up over many uses. Most examples in Ireland date to the Bronze Age, roughly 1500 to 500 BC, though some have earlier or later dates. The name, loosely translated from Irish, is sometimes rendered as "cooking place of the deer" or "cooking place of the wild animal", though the etymology has been debated. Alternative theories have proposed uses ranging from textile processing to bathing, and experimental archaeology has tested several of these with some success. Cork is particularly dense with recorded examples, making sites like the one at Killeens part of a broader pattern rather than an isolated curiosity.