This is a fulacht fia, a type of ancient cooking site found in great numbers across Ireland, typically Bronze Age in origin. The mound itself is the accumulated waste, burnt stone and charcoal, thrown aside after repeated use, and it is this debris that survives when almost everything else has vanished.

The mound at Gortnascregga is roughly oval in shape, measuring fifteen metres east to west and just under thirteen metres north to south, with a height of just over a metre. It narrows towards its eastern end, giving it a slightly tapered profile. The standard interpretation of such sites involves a trough, usually timber-lined or cut into the ground nearby, which would have been filled with water and heated by dropping fire-heated stones into it. The stones crack and shatter with repeated thermal shock and become useless for further heating, so they are discarded to the side, building up over time into exactly the kind of low, burnt-material mound visible here. Whether the primary purpose was cooking, bathing, textile processing, or some combination of these remains a matter of ongoing discussion among archaeologists.