That is, in a sense, the point. Somewhere in the marshy ground on the western bank of a stream in north Cork, a fulacht fia lies buried without a trace visible at the surface. A fulacht fia is a type of prehistoric cooking or processing site, typically identified by a horseshoe-shaped mound of fire-cracked stones and charcoal, built up over many uses beside a reliable water source. At Ballybahallagh, even that modest monument has disappeared into the bog.

The site appeared on a 1937 Ordnance Survey six-inch map as a mound, which suggests it was at least partially visible within living memory of that survey. By the time it was formally recorded, however, no surface trace remained. It is thought to be one of ten fulachta fiadh in the immediate area documented by a researcher named Bowman in 1934, suggesting the landscape around this stream was once used repeatedly and perhaps intensively for whatever purposes these sites served, whether cooking, bathing, or some form of craft activity involving heated water. The concentration of ten such sites in one locality is itself notable; fulachta fiadh are common across Ireland, but clusters like this hint at a particular attachment to a specific stretch of ground over a long period.

The marshy, waterlogged conditions that swallowed the mound are likely the same conditions that preserved whatever organic remains lie beneath, should the site ever be excavated. For now it remains one of those places where the archaeology exists entirely below ground and below notice, its location fixed on old maps but invisible to anyone standing beside the stream today.