It is about ten metres across and less than a metre high, overgrown, with a shallow depression at its centre. Nothing about it announces itself. And yet that depression is the clue: this is a fulacht fia, one of the most common prehistoric monument types in Ireland, and the hollow in the middle is where the action once happened.

A fulacht fia is a burnt mound, typically dating to the Bronze Age, and the type is found in the hundreds across Ireland. The working theory, supported by experimental archaeology, is that these sites were used for cooking or possibly for other heat-based processes. The basic method involved heating stones in a fire until they were near-cracking hot, then dropping them into a water-filled trough to bring the water to a boil. Over time, the discarded shattered stone accumulated into the characteristic horseshoe or circular mound of blackened, heat-fractured material that survives today. The depression at the centre of the Lisbealad example corresponds to where that trough would have sat. The proximity to the Glasheenahielan River is no coincidence; water supply was essential, and fulachtaí fia are almost always found close to a reliable source.