To a casual eye it looks like little more than a slight rise in the bog, but it is almost certainly a fulacht fia, one of the most common prehistoric monument types in Ireland and one of the least obviously dramatic. A fulacht fia is essentially a cooking site: a trough dug into wet ground, filled with water, and heated by dropping fire-cracked stones into it. Those shattered, heat-blackened stones accumulate over repeated use into a horseshoe-shaped mound, and it is precisely that kind of spread which survives at Knoppoge.

The site was noted by Bowman in 1934, who recorded two fulachta fiadh on land then belonging to a D. Vaughan. The marshy, well-side location is entirely typical of the type; access to a reliable water source was essential to the whole process, and low-lying wet ground tends to preserve the burnt stone deposits better than drier soils. Fulachta fiadh are generally dated to the Bronze Age, broadly between 1500 and 500 BC, though the tradition may have persisted later in some areas. Their exact function is still debated, with cooking remaining the most widely accepted explanation, though proposals have ranged from bathing and textile processing to brewing.