They appear as low, horseshoe-shaped mounds, typically beside a stream or in boggy ground, and represent the burnt and discarded remnants of a cooking method used repeatedly over centuries. The basic principle involved heating stones in a fire, dropping them into a water-filled trough until the water boiled, and using that trough to cook meat. The stones, cracked and shattered by the thermal shock, were piled to the side after each use, and it is those accumulated heaps of fire-cracked stone that survive in the landscape today. The site at Carrownaraha, in County Mayo, is one such monument, quietly present in the western Irish landscape.

The term fulacht fia translates loosely from the Irish as something like "cooking pit of the wild" or "cooking place of the deer", and most examples date to the Bronze Age, roughly 1500 to 500 BC, though some continued in use into the early medieval period. Their distribution across Ireland is remarkable, with estimates running to tens of thousands of recorded sites, yet individual examples rarely carry the kind of documentary history that attaches to castles or churches. They leave no inscriptions, no coats of arms, no names. What they offer instead is a direct and material link to the daily rhythms of prehistoric life, the labour of gathering fuel, heating stone, and preparing food in a landscape that would have looked very different from the one we see now. Mayo, with its extensive boglands, is particularly rich in such survivals, the acidic, waterlogged conditions having preserved both the mounds and, in some excavated cases, the wooden troughs themselves.