It rises just 0.27 metres above the surrounding ground, and yet it spans roughly 36 metres from north-west to south-east and 30 metres from north-east to south-west. What looks at first like a modest rise in a ploughed field is in fact a fulacht fia, one of the most common prehistoric monument types found in Ireland. A fulacht fia is essentially an ancient cooking or heating site, typically consisting of a trough, a hearth, and a mound of heat-shattered stone left over from repeatedly heating rocks and plunging them into water to boil it. They are found in their thousands across the country, almost always near water, and almost always dating to the Bronze Age.

The proximity to the pond here is entirely typical. Water was the whole point. Stones would be heated in a fire until red-hot, then dropped into a water-filled trough, where they cracked and fragmented from the thermal shock. Over time, the discarded burnt and broken stones accumulated into the distinctive horseshoe-shaped mound that archaeologists now recognise as the signature of these sites. At Poulleagh, that mound has been considerably flattened and spread by centuries of ploughing, which accounts for its unusually wide footprint relative to its modest height. The shape that survives is a ghost of what would once have been a more defined and prominent feature.