It is easy to walk past without recognising it for what it is, but the horseshoe shape is a giveaway: this is a fulacht fia, one of the most common yet least celebrated monument types in the Irish landscape.

A fulacht fia is, in essence, the remains of a prehistoric cooking place. The typical method involved heating stones in a fire until they were red-hot, then dropping them into a water-filled trough to bring it rapidly to the boil. The broken, fire-cracked stones were thrown aside after each use, and over time these accumulated into the characteristic horseshoe-shaped mound that surrounds the trough on three sides. At Barnacahoge, the mound measures roughly 12 metres along its longer axis and rises to about 1.4 metres at its western edge. The material it is built from, heat-shattered stones packed into charcoal-rich soil, is exactly what centuries of repeated burning and boiling would leave behind. A hollow area between the arms of the mound, opening to the west-northwest towards the stream, may mark where the trough itself once sat. The stream nearby would have provided the water supply. Fulachtaí fia are generally dated to the Bronze Age, though some sites were used across multiple periods, and their precise function, whether purely culinary, used for bathing, or something else entirely, remains a matter of debate among archaeologists. A later field wall has clipped the southern edge of the mound, a small indignity that speaks to centuries of agricultural activity layering itself over far older remains.