It measures roughly eight metres long, seven metres wide, and barely forty centimetres high, and to a passing eye it might register as nothing more than a slight rise in a wet field. What it actually represents is a fulacht fia, one of the most common yet persistently mysterious monument types in Irish archaeology.

A fulacht fia is essentially a Bronze Age cooking site, or at least that is the most widely accepted interpretation. The characteristic mound is composed of burnt and fire-cracked stone, the discarded debris from a process in which stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. Thousands of these sites survive across Ireland, and they cluster reliably near water sources and low-lying wet ground, exactly the kind of setting this example occupies beside the Ahadallane River. The horseshoe or oval shape of the mound is typical, formed as spent stones were thrown aside from a central working area over repeated use. Some researchers have proposed alternative functions, including brewing or textile processing, though the cooking explanation remains the most common. The Rathcoola example follows the classic pattern closely, its modest height reflecting the gradual accumulation of shattered, heat-exhausted stone rather than any deliberate construction.