It is, in fact, the remains of a fulacht fia, a type of prehistoric cooking or industrial site found in enormous numbers across Ireland, typically identified by the characteristic horseshoe-shaped mound of fire-cracked stone and charcoal that accumulates around a central trough. The mound here is modest in height, just 0.3 metres, but spreads to over fourteen metres in length and more than seventeen metres in width, suggesting repeated and sustained use over time.

The mechanics of a fulacht fia are straightforward once you know them. Stones were heated in a fire and then dropped into a water-filled trough, bringing the water rapidly to a boil. The stones, unable to withstand repeated thermal shock, cracked and fragmented and were discarded to the side, building up the distinctive mound that survives today. The proximity of this example to a natural spring is entirely typical; these sites almost always cluster near reliable water sources. What makes the Killeen location particularly interesting is that it does not stand alone. Two further fulachta fiadh lie close by, one to the north and one to the south, suggesting this stretch of ground saw concentrated activity during prehistoric times, possibly indicating a routeway, a gathering place, or simply a particularly convenient water supply that drew people back again and again.