It is roughly eighteen metres across and barely half a metre high, its surface long since grassed over. What lies beneath is considerably older and stranger: a dense accumulation of burnt and fire-cracked stone, the signature residue of a fulacht fia.

A fulacht fia is a type of prehistoric cooking or processing site found across Ireland and Britain in remarkable numbers. The usual interpretation is that stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil, a method that works efficiently despite its apparent simplicity. The shattered, heat-stressed stones were then raked aside after use, and over repeated visits this discarded material built up into the characteristic horseshoe-shaped or circular mound that survives today, often with a hollow at the centre where the trough once sat. The Clonmoyle example follows this pattern closely: the central hollow is still visible, and the burnt material extends to a depth of around half a metre, as exposed in the stream bank where drainage works disturbed the northern edge of the mound. That disturbance, while unfortunate from a preservation standpoint, at least offers a rare cross-section through the accumulated debris, making the internal composition directly visible rather than a matter of inference.