The example uncovered at Mullaghavorneen, Co. Longford adds a detail that sets it slightly apart: the trough beneath the mound is unusually large, and the people who used it appear to have built some kind of structure around it.

A fulacht fia, to use the Irish term, is a prehistoric cooking or processing site, typically consisting of a water-filled trough into which heated stones were dropped to bring the water to a boil. The stones fracture with the thermal shock, and it is the accumulated dumps of this shattered material that form the characteristic horseshoe-shaped mounds still scattered across the Irish countryside. This particular site was first identified in 2001 when topsoil-stripping for a quarry extension exposed the remains, and a formal excavation followed in 2004. The mound itself measured three metres long, three metres wide, and roughly thirty centimetres deep. Beneath it lay a trough measuring two and a half metres by two metres and thirty-five centimetres deep, dimensions that place it at the larger end of the scale for features of this type. More intriguing still were four post-holes, one at each corner of the trough. The excavator, Read, proposed in subsequent reports that these may have supported a shelter of some kind, either a covering over the trough or a more substantial enclosure around the whole working area. Whether that structure served a practical purpose, keeping rain out of the water or retaining heat, or whether it had some other significance, cannot be determined from what remains. A second area of burning, recorded as a spread of burnt material, lies approximately fifty metres to the south-south-west, suggesting that activity in the vicinity was not confined to a single spot.