Roughly eighteen metres across from east to west and fourteen from north to south, it is composed almost entirely of burnt and fire-cracked stone, the accumulated debris of repeated heating over what may have been centuries. To pass it without knowing what it was would be easy enough; it looks, at most, like a gentle rise in damp ground.

The mound belongs to a class of prehistoric monument known as a fulacht fia, one of the most common archaeological features in the Irish countryside and one of the least understood. The basic mechanics are reasonably clear: a trough, typically lined with wood or stone and dug close to a water source, would be filled with water, then heated by dropping fire-cracked stones into it. The stones, once spent and shattered by the thermal shock, were discarded to the side, building up over time into the distinctive horseshoe-shaped mound that survives in so many low-lying and wet locations today. What the troughs were actually used for, whether cooking, bathing, textile processing, or some combination of purposes, remains a matter of genuine debate among archaeologists. Most fulachta fiadh date to the Bronze Age, broadly speaking the period from around 2500 to 500 BC, though some sites show evidence of use across long stretches of time. The Scarteen example sits in marshy ground, exactly the kind of waterlogged setting these monuments consistently favour, where a reliable water source would have been close at hand and the accumulation of burnt stone has helped preserve the site's outline to the present day.