What was once a roughly circular mound of burnt stone and charred material, some 22 metres long and 17 metres wide, is now horseshoe-shaped, open on its south-western side. The reason for that missing arc is mundane in the worst possible way: sometime around 1974, material was scooped from the mound and used for road building.

The site is a fulacht fia, a type of prehistoric cooking place found in enormous numbers across Ireland. The typical arrangement involved a trough filled with water, heated by dropping fire-cracked stones into it until the water boiled, and then used to cook meat. The spent, heat-shattered stones were discarded to the sides, building up over repeated use into the horseshoe-shaped or crescent mounds that survive today. At Lismire, a shallow indentation about 1.8 metres across marks where a well once stood adjacent to the mound, though it has long since gone dry. That well would have been the water source at the heart of the site's original function. A ringfort lies roughly ten metres to the south, a proximity that is not unusual; fulachta fiadh are often found close to later settlement features, though the two do not necessarily date from the same period. The second depression on the south-western side, measuring roughly 8 by 9.5 metres, is the direct scar left by the road-building removal, a gap large enough to suggest that a significant portion of the accumulated burnt material was taken before anyone intervened.