It measures roughly fifteen metres north to south and sixteen metres east to west, rising only about three-quarters of a metre above the surrounding pasture, with a wide opening of just over three metres facing west. Unassuming to the point of near-invisibility, it is exactly the kind of feature that a walker might cross without a second thought.

This is a fulacht fia, a type of site found in enormous numbers throughout Ireland, typically dating from the Bronze Age, though some were in use into the early medieval period. The name, loosely translated from the Irish, refers to a cooking place, and the mechanics were straightforward: a trough, usually timber-lined or cut into the ground nearby, would be filled with water, and stones heated in a fire would be dropped in to bring it to the boil. The spent, shattered stones were then discarded to the sides, accumulating over repeated use into the characteristic horseshoe or kidney-shaped mound that survives today. The burnt, fragmented stone that gives these mounds their distinctive dark colour is sometimes called "burnt mound material", and it is this accumulation at Garrane, built up through many separate episodes of use, that forms the mound still visible in the pasture. Whether the site was used purely for cooking meat, for bathing, for textile processing, or for some combination of purposes remains a subject of ongoing discussion among archaeologists.