It is, in fact, a fulacht fia, one of the most common yet still somewhat puzzling monument types in the Irish landscape. The characteristic horseshoe shape comes from the accumulated spoil of burnt and shattered stone, crescent-like banks that build up over repeated use around a central trough.

Fulachtaí fia are generally dated to the Bronze Age, though some remained in use into the early medieval period. The working principle was straightforward: a trough, often timber-lined or cut into the earth, was filled with water, and stones heated in a nearby fire were dropped in to bring it to the boil. The burnt, heat-fractured stones were then raked out and piled to the sides, gradually forming the mound that survives today. What exactly these sites were used for remains debated. Cooking is the long-standing explanation, and experiments have shown the method works well for boiling meat, but some researchers have proposed uses ranging from textile processing to bathing. The location here, beside a spring in marshy ground, fits the pattern seen at many such sites across Ireland, where a reliable water source was clearly a prerequisite. The spread of burnt material noted at Beheena is consistent with prolonged or repeated episodes of use, the physical residue of whatever activity drew people back to this particular wet corner of the Cork countryside. By 1938, when the Ordnance Survey recorded it on their six-inch map, the mound's distinctive shape was still clear enough to be mapped, which speaks to how durable these stone-and-earth accumulations can be.