This is a fulacht fia, a type of site found in the hundreds across Ireland, typically dating from the Bronze Age. The basic technology was straightforward: a trough dug into wet ground, filled with water, and heated by dropping fire-cracked stones into it. The shattered, heat-spent stones were then thrown aside, and over generations of repeated use they accumulated into the horseshoe-shaped mounds that survive today. The mound at Dromgarriff, heavily overgrown now, measures roughly thirteen metres in length and just over twelve and a half metres wide, making it a fairly substantial example of the type.

The choice of marshy ground was deliberate rather than incidental. A high water table meant the trough would stay naturally filled, reducing the labour involved in hauling water. This is why fulachtaí fia cluster so reliably in low-lying, boggy terrain across the Irish countryside, often invisible until you are almost standing on them. At Dromgarriff, that waterlogged setting has helped preserve the mound while simultaneously encouraging the dense overgrowth that now obscures it. The burnt material beneath the vegetation is the defining signature: cracked, reddened stone and charcoal-flecked soil that accumulates nowhere else quite like this.