It is the kind of feature that a walker might step over without a second thought, mistaking it for a natural rise in the ground. It is not. What lies beneath the vegetation is a fulacht fia, one of thousands of such sites scattered across Ireland, and one of the more quietly persistent mysteries in the Irish archaeological record.

A fulacht fia is, in its simplest form, a burnt mound. The typical interpretation is that these sites functioned as ancient cooking places, probably from the Bronze Age onwards, where water was heated by dropping fire-cracked stones into a trough. The stones, once shattered by repeated heating and cooling, were discarded into a horseshoe-shaped mound around the trough. Over centuries, these mounds of fractured, fire-blackened material accumulated to considerable size. Their association with streams and wet ground is almost universal, which makes the location here, beside a watercourse in low-lying grazing land, entirely characteristic. The burnt material visible in the mound at Kilberrihert is the accumulated residue of that process, however many times it was repeated and over however long a period.