The site is a fulacht fia, a type of prehistoric cooking or heating site found across Ireland, typically identified by a crescent-shaped mound of fire-cracked stone and charcoal left behind after repeated episodes of heating water by dropping hot stones into a trough. This one, at Kellymount, was more complex than most.

The excavation was carried out under licence in advance of road improvement works on the N9/N10 Kilcullen to Waterford route, which means it was only uncovered at all because of modern civil engineering. The burnt spreads extended up to twelve metres by eight metres at their largest, and beneath them lay a cluster of features arranged around a central waterhole measuring roughly seven metres by six metres, and reaching a depth of around six metres. That waterhole appears to have been the focal point of the whole site, with troughs and pits gathered around it. The easternmost trough, sub-rectangular and small enough to stand beside comfortably, had three stake-holes in its base suggesting it was once timber-lined; radiocarbon dating placed its use somewhere between 2399 and 2154 cal BC, squarely in the Early Bronze Age. A second trough nearby was likely associated with it, though it produced no datable material. The two pits to the west of the waterhole told a different story: one of them, ringed with 22 stake-holes, returned a radiocarbon date of 751 to 409 cal BC, placing it in the Iron Age, centuries after the first trough had gone out of use. A second pit had 35 tightly spaced stake-holes around the perimeter of its base and remained undated. An arc of stake-holes between the two troughs may indicate that a windbreak of some kind once stood there, shielding the working area from the prevailing conditions. The site, then, was not a single episode of ancient activity but a place returned to across a span of perhaps fifteen hundred years or more.