A fulacht fia is essentially a burnt mound: the accumulated remains of a repeatedly used outdoor cooking method in which stones were heated in a fire and dropped into a water-filled trough until the water boiled. Over time, the shattered, heat-cracked stones pile up into a characteristic horseshoe or kidney-shaped spread. At Knockballymartin, that spread measures roughly 13.5 metres by 12.5 metres, still visible as a grass-covered rise in open pasture on the southern bank of a stream.

What makes the site at Knockballymartin quietly arresting is not the mound itself but its company. Within a stretch of roughly 340 metres of the same ground, four more fulachtaí fia have been recorded, strung out to the north and north-east at intervals of 150, 170, 260, and 340 metres respectively. Whether they represent the same community returning to a favoured corridor near water across many generations, or several distinct groups each choosing the same sensible spot beside a reliable stream, is not something the surface evidence alone can answer. The clustering is nonetheless unusual, and suggests that this particular valley floor held some persistent attraction for prehistoric activity over a long period. Fulachtaí fia are broadly dated to the Bronze Age, roughly 2000 to 500 BC, though some examples in Ireland fall outside that range, and without excavation the individual mounds at Knockballymartin cannot be dated more precisely than that general bracket.