That, in a way, is precisely what makes it worth knowing about. Somewhere beneath the ground near a drainage channel in mid Cork lies a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, yet almost entirely invisible in the modern landscape. The fulacht fia typically consisted of a trough dug into the earth, lined with timber or stone, which was filled with water and heated by dropping fire-cracked stones into it. The broken, heat-shattered stones accumulated over repeated use into a horseshoe-shaped mound beside the trough. At An Tseanchluain, even that mound has vanished, leaving no surface trace whatsoever.

Fulachtaí fia are among the most common archaeological monument types in Ireland, with thousands recorded, and Cork is particularly dense with them. They date mostly to the Bronze Age, roughly 1500 to 500 BC, though some earlier and later examples are known. The one at An Tseanchluain was identified from a map produced by the archaeology department at University College Cork, recorded under the Irish form of the name, fulacht fiadh, and its position on the edge of a drainage channel fits a pattern well established across the country: these sites are almost always found in low-lying, wet ground near water sources, which were essential to their function. The drainage channel itself may have altered or obscured whatever visible remains once existed.