This is a fulacht fia, a type of ancient burnt mound found in extraordinary numbers across Ireland, particularly in low-lying, waterlogged ground near streams. The classic interpretation is that they served as cooking sites: stones were heated in a fire, dropped into a water-filled trough, and used to bring the water to the boil. The mound itself is the accumulated debris of cracked and discarded stones, left behind after repeated use over what were sometimes very long periods.

This particular example sits on the northern side of a stream, which by 1935 had reduced to a shallow linear depression crossing the field, visible mainly as a slight change in the ground surface. The burnt spread measures roughly 18 metres along a northwest to southeast axis and about 8 metres across, with its opening facing approximately north-northeast, the characteristic hollow of the original trough or working area still legible in the kidney shape of the mound. What makes the Corrin site especially interesting is that it does not stand alone. Approximately 25 metres to the southwest, on the opposite bank of the same stream, lies a second, closely similar spread. Two fulachtaí fia facing each other across a watercourse suggests either repeated use of a favoured location over time, or the possibility that both were in use during the same period, exploiting the same water source from either side.