It is, in fact, a fulacht fia, one of the most common and least understood monument types in the Irish landscape. These horseshoe-shaped mounds, found in their thousands across the country, are the remnants of prehistoric cooking sites, where stones were heated in fire and then dropped into a trough of water to bring it to a boil. The broken, fire-cracked stones, discarded after use, gradually accumulated into the characteristic mound shape that survives today.

This particular example at Carrowkeel measures roughly 9.3 metres along its northwest to southeast axis and around 11 metres across, rising to between 0.6 and 1 metre in height. A central depression, about 1.6 metres wide, opens to the northeast, facing directly out onto the boggy expanse beyond. That orientation is unlikely to be accidental; proximity to standing water was essential to the function of these sites, and the low-lying wet ground stretching away to the north and northeast would have supplied exactly what was needed. Where the mound has been exposed, the tell-tale signs of prehistoric activity are visible: shattered stone fragments embedded in black, charcoal-rich peaty soil, and large pieces of charcoal showing at the southeastern arm of the U-shape. The southwestern end of the mound backs up against rising ground, tucked into the scarp as though fitted to the natural contour of the land. About 25 metres to the south-southeast, an ancient road or trackway runs out through the bog, suggesting this was once a purposeful, connected place rather than a remote margin.

Brambles now cover much of the mound, obscuring its full extent and making close inspection difficult. The site sits in pasture, and the combination of vegetation and low relief means it reads more as a slight swelling in the field than anything immediately remarkable.