Beneath the turf lies a spread of burnt and heat-shattered stone roughly ten metres north to south and six metres east to west, the quiet signature of a fulacht fia.

A fulacht fia is a prehistoric cooking site, typically consisting of a trough dug into the ground, a hearth for heating stones, and the accumulated mound of cracked, fire-blackened rock that builds up over repeated use. The method is straightforward: stones are heated in a fire and dropped into a water-filled trough until the water boils. The stones fracture with the thermal shock and are then discarded, gradually forming the horseshoe-shaped or oval spreads that survive in the landscape today. These sites are found in their thousands across Ireland, most commonly dating to the Bronze Age, and they cluster reliably near water, which is exactly what the location at Mashanaglass reflects. The stream nearby was not incidental; it was the point of the whole enterprise.