It is the trace of a fulacht fia, one of Ireland's most common yet least understood prehistoric monument types, and its position beside a water source is no accident.

Fulachtaí fia, found in their thousands across Ireland, are generally understood to have functioned as cooking sites, most likely during the Bronze Age. The typical arrangement involved a trough, usually timber-lined or stone-lined and filled with water from a nearby spring or stream, into which stones were heated in a fire and then dropped to bring the water to a boil. Over repeated use, the burnt and shattered stones were raked out and piled to the sides, forming the distinctive horseshoe-shaped mound that survives at many sites. At Garraun, the spread of burnt material visible in the tillage ground is the remnant of precisely this kind of accumulation, the discarded evidence of fires lit and stones cracked, probably across many individual episodes of use. The proximity to a spring fits the pattern closely; a reliable, clean water source was essential to the whole process.