It rises only about 28 centimetres above the surrounding ground, measures roughly 16 metres north to south and 15 metres east to west, and consists almost entirely of burnt and shattered stone. To a passing eye it might read as a natural feature, or a field clearance dump. In fact it is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, and one of the more quietly persistent traces of organised human activity in the Irish landscape.

Fulachtaí fia, the plural form, typically date from the Bronze Age, though some have earlier or later phases of use. The basic technology involved heating stones in a fire and then dropping them into a water-filled trough to bring the water to a boil, a process that cracks and blackens the stones and, over repeated use, builds up the distinctive horseshoe-shaped or oval mounds of burnt material that survive today. At Knockballymartin, the site sits roughly 100 metres west of a stream, which would have provided the necessary water supply. On the south-east side of the mound, a patch of noticeably richer grass growth, about 8 metres east to west and 2 metres north to south, suggests the location of the original trough, where organic material and retained moisture have continued to feed the soil long after the trough itself ceased to function. It is a small but telling detail: the activity of several thousand years ago still leaving a faint signature in the vegetation above it.