What gives it away is a cross-section of burnt material exposed in a drain dug to deepen a nearby stream bed, a small window into something much older lying just beneath the surface. The site is a fulacht fia, a type of ancient cooking or processing site found across Ireland and Britain, typically consisting of a mound of fire-cracked stones and charcoal accumulated beside a water source over repeated use. The general form involves heating stones in a fire, then dropping them into a water-filled trough to bring it to the boil, a method that leaves behind a distinctive signature of shattered, heat-reddened stone.

Fulachtaí fia are most commonly associated with the Bronze Age, roughly 1500 to 500 BC, though some date earlier or later. They tend to cluster near wetlands and running water, which made the site at Carrigacooleen, set in marshy ground with a stream close by, entirely typical in its positioning if not especially visible from the surface. The burnt material now exposed in the drain section is essentially what remains of those repeated episodes of heating and discarding stone, compressed into the earth and preserved by the damp conditions that surround it. Such sites are often discovered precisely this way, through drainage works or road improvements that cut unexpectedly into the accumulated debris of prehistoric activity.