It is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, typically dating from the Bronze Age. The basic principle was straightforward: water was collected or channelled into a trough, stones were heated in a fire and then dropped into the water to bring it to a boil, and the cracked, heat-shattered fragments were raked out and discarded. Over time, those discarded stones accumulated into the characteristic horseshoe-shaped mound that survives today at thousands of sites across the country.

The mound at Barrahaurin measures roughly eight metres along its northeast to southwest axis and six metres across the other way, rising to about a metre in height. Its opening, just over a metre and a half wide, faces southeast, and the southwest arm of the horseshoe stands noticeably higher than the northeast. The proximity to a stream is entirely typical; a reliable water source was essential to the whole operation, and fulachtaí fia are almost always found close to running water or boggy ground. The asymmetry between the two arms is a small but telling detail, the kind of irregularity that accumulates naturally when material is piled by hand over repeated use rather than built to a plan.