It is a fulacht fia, a type of prehistoric cooking site found in great numbers across Ireland, and one of the more understated categories of monument in the Irish landscape. The typical fulacht fia consists of a horseshoe-shaped mound of fire-cracked stones, the discarded residue of repeated heating. Stones would have been placed in a fire, then dropped into a water-filled trough to bring it rapidly to boiling point. Over time, the shattered and spent stones accumulated into the characteristic mound that survives today.

These sites date broadly to the Bronze Age, with many examples clustered between roughly 1500 and 500 BC, though some are earlier. They tend to appear near water sources, a practical necessity given the volume of liquid involved in the process, and are often found in low-lying or gently sloping ground of exactly the kind described here. Their precise function has been debated at length; cooking is the most widely accepted explanation, but proposals have ranged from textile processing to bathing. The Glenleigh example preserves the essential form: a spread of burnt stone and organic material, sealed beneath turf, slowly dissolving back into the hillside.