The opening of the horseshoe faces north, towards a stream, and where that stream has been cutting into the mound's western edge it has laid bare what lies inside: heat-shattered stones and soil dark with charcoal. That combination of materials is the signature of a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland. The basic principle involves heating stones in a fire, dropping them into a water-filled trough until the water boils, and using the resulting heat to cook meat. The cracked and spent stones, discarded after repeated heating and cooling, accumulate over time into exactly the kind of mound visible here.

The Coomdeeween mound measures roughly 14.7 metres east to west and just under 8 metres north to south, rising to about 1.6 metres at its highest point, which places it among the more substantial examples of its type. Fulachtaí fia are generally associated with the Bronze Age, though the precise function of individual sites has long been debated, with some researchers arguing that at least some served purposes beyond cooking, including bathing or textile processing. What makes the setting here quietly compelling is the clustering of monuments in a small area: an enclosure lies approximately 20 metres to the south, and an unclassified megalithic tomb sits around 70 metres to the south-east. A megalithic tomb is a prehistoric stone-built funerary structure, and the presence of one so close to a cooking site and an enclosure suggests this particular hillside above the Carhan valley was a place of sustained human activity across a long stretch of prehistory.