It is a fulacht fia, one of thousands of such sites scattered across Ireland, and the shape and setting give it away to those who know what to look for. The horseshoe form is characteristic: a trough would once have occupied the open centre, filled with water that was heated by dropping fire-cracked stones into it. Those stones, shattered and blackened by repeated heating and cooling, were raked aside into the surrounding mound. Repeated use over generations built up the distinctive curved bank of burnt and fragmented material that survives today.

Fulachtaí fia are generally dated to the Bronze Age, roughly 1500 to 500 BC, though some sites have produced earlier or later dates. Their precise function has long been debated; cooking is the most widely accepted explanation, though brewing, textile processing, and bathing have all been proposed at various points. What nearly all of them share is a preference for low-lying, wet ground close to a water source, which made refilling the trough straightforward. The Rylane River would have served exactly that purpose here, and the marshy conditions that make the site awkward to approach today are likely the same conditions that made it a practical location in prehistory. The site is now overgrown, its mound softened by vegetation.