A fulacht fia is a type of burnt mound, one of the most common archaeological monuments in Ireland, and the principle behind it is straightforward: stones were heated in a fire and dropped into a water-filled trough, bringing the water to a boil for cooking. The example at Ballintotty in County Tipperary, found during advance monitoring for the Nenagh Bypass, preserved that process in unusual detail.

The main feature was a low, horseshoe-shaped mound of fire-cracked stone, roughly 16 metres by 9 metres and no more than 40 centimetres deep, the accumulated debris of repeated heating and discarding. At its centre sat an unlined rectangular trough, approximately 2.4 metres long, 1.2 metres wide, and 0.32 metres deep, still filled with burnt stones when excavated. Post-holes at each internal corner of the trough suggest it was once timber-lined or shuttered, and a shallow linear cut running beside a possible pot-boiler feature on the north-west edge has been interpreted as the remains of a windbreak, shielding the working area from the elements. About ten metres to the south-east, excavators found a second, oval spread of burnt stone, smaller and shallower, beneath which lay further pits and clusters of stake-holes. Between the two sites, a metalled stone surface connected some of the pits, suggesting a path or working surface linking the two activity areas. Finds were sparse but telling: small quantities of animal bone and teeth, a few chert flakes, unworked wood, and charcoal. The bones hint at butchery or feasting; the chert and wood are quieter traces of the people who worked here, their identities otherwise unrecorded.