This is a fulacht fia, a term used for the fire-cracked mounds that appear in their thousands across the Irish landscape, typically beside water and invariably damp underfoot. The current thinking is that they served as cooking sites, where stones were heated in a fire and then dropped into a trough of water to bring it to a boil, though some archaeologists have proposed additional uses including textile processing or bathing. The burnt and shattered stones, discarded after repeated heating and cooling, built up over time into the characteristic horseshoe shape that defines the type.

The mound at Cooles follows that shape closely. It measures roughly 10.7 metres on its northeast to southwest axis and 9.4 metres across, rising to about half a metre in height, with an opening of approximately 3.5 metres facing southeast. That southeast-facing gap is where the trough would have sat, positioned to take advantage of the nearby stream and the natural lie of the ground. The marshy conditions that make the spot feel slightly inhospitable today are precisely what made it useful then: reliable water, close at hand. The mound is partially overgrown now, its profile softened by grass and scrub, but the horseshoe outline remains legible in the field.