Just under a metre high and roughly ten metres across, it is composed almost entirely of burnt and fire-cracked stone, the signature remains of a fulacht fia. The name, from Old Irish, refers to a type of prehistoric cooking site found in enormous numbers across Ireland, typically Bronze Age in date, and almost always positioned close to a water source. The principle was straightforward: stones were heated in a fire, then dropped into a water-filled trough to bring it to a boil, cooking meat or, as some researchers have argued, serving other purposes such as bathing or textile processing. Over time the shattered, heat-spent stones were raked out and piled up, forming exactly the kind of low, horseshoe-shaped or oval mound visible here at Knockearagh.

The mound is partially overgrown now, measuring 10.8 metres east-northeast to west-southwest and 8.6 metres north-northwest to south-southeast, its burnt material slowly being reclaimed by grass and scrub. Its proximity to the stream is no accident. Fulachtaí fia, which number in the thousands across the Irish landscape, cluster persistently near reliable water sources, and the positioning of this one fits the pattern precisely. The site survives in rough grazing land, which, while not offering formal protection from agricultural improvement, has at least meant it has not been ploughed out entirely.