This is a fulacht fia, a type of prehistoric burnt mound found in considerable numbers across Ireland, typically beside water sources. The method involved heating stones in a fire, dropping them into a water-filled trough to bring it rapidly to the boil, and using that heat to cook meat. The crescent shape so characteristic of these sites comes from the gradual accumulation of discarded, fire-cracked stones piled up around the trough over repeated use.

The mound at Knockfobole measures roughly 18 metres along its wider axis and 9 metres across, with its open end facing north-north-west and a slight raised lip still visible at the edge of what would have been the trough area. The rear of the mound, at the south-south-east, stands about 0.9 metres high and extends some 3.5 metres in width, giving a sense of how much shattered stone accumulated here over its working life. The site sits in improved pasture, with a wet area and drainage channels running to the north and south, exactly the kind of low-lying, water-adjacent ground that fulacht fia builders consistently favoured. Whether the water source is natural or has been altered by later land improvement is not clear, but the proximity of moisture to the site is consistent with how these monuments were used and sited across the Irish landscape.