It measures about 9.5 metres on its longer axis and rises to just under a metre in height, with its opening facing south-west toward the water. To the untrained eye it reads as an unremarkable rise in the ground. To an archaeologist, it is immediately recognisable as a fulacht fia, one of the most widespread and still partially mysterious monument types in the Irish landscape.

A fulacht fia is, in essence, the debris left over from a prehistoric cooking method. The typical process involved heating stones in a fire, then dropping them into a water-filled trough to bring it rapidly to the boil. The stones, repeatedly cracked by thermal shock, were discarded after use, and over generations the pile of fragmented, fire-blackened material grew into a low mound, often horseshoe or kidney-shaped, almost always located close to a water source. Thousands of these monuments survive across Ireland, dating mostly from the Bronze Age, roughly 2000 to 500 BC, though some have been identified as earlier or later. Whether they served purely as cooking sites, or also as places for bathing, textile processing, or communal gathering, remains a matter of genuine debate among researchers. The example at Barleyhill fits the classic profile precisely: the proximity to the stream, the characteristic shape, the southward-facing opening that would have given convenient access to both fire and water.