It is a fulacht fia, a type of prehistoric cooking site found in their thousands across Ireland, and this one at Ballinphellic sits in the characteristic horseshoe shape that makes the type recognisable once you know what you are looking at. The mound measures seventeen metres in length, twelve in width, and rises to about a metre and a half, with an opening five metres wide facing west-north-west. Partially overgrown now, it holds its form quietly in the grass.

Fulachtaí fia, the plural form, are among the most common archaeological monuments in Ireland, dating mostly to the Bronze Age, roughly 1500 to 500 BC, though some examples are older or younger. The basic principle behind them is straightforward: a trough was dug near a water source, lined to hold water, and stones were heated in a fire before being dropped in to bring the water to a boil. The discarded, shattered stones accumulated over time into the distinctive horseshoe mound that frames the former trough. What they were actually used for remains a matter of debate among archaeologists, with cooking the most widely accepted explanation, though brewing, hide-working, and bathing have all been proposed. The proximity of the Ballinphellic example to a stream fits the pattern almost perfectly, since a reliable water supply was essential to the whole operation.