Where a drainage channel cuts through the ground, a dark smear of burnt material is visible in the exposed section, the telltale signature of a fulacht fia, one of the most common yet least understood monument types in the Irish landscape.

A fulacht fia is essentially a prehistoric cooking site, typically Bronze Age in date, consisting of a trough dug into the ground, a hearth, and a mound of fire-cracked stones. The working method involved heating stones in a fire and dropping them into a water-filled trough to bring it to boiling point, a process that slowly builds up the characteristic horseshoe-shaped mound of discarded, shattered stone that survives at so many sites across Ireland. The burnt material visible at Barrafohona is consistent with exactly this kind of activity, the charred and heat-fractured debris that accumulates over repeated use. North-facing slopes with their tendency toward damp, poorly drained ground were apparently favoured locations, likely because a ready water supply was essential to the whole process.