A fulacht fia, sometimes called a burnt mound, is the remains of an ancient outdoor cooking site: a trough dug into the ground would be filled with water, and stones heated in a nearby fire were then dropped in to bring the water to a boil. Over repeated use, the cracked and shattered stones were raked aside, building up the characteristic horseshoe-shaped midden of burnt and blackened material that still survives today.

This particular example measures 12.5 metres in length and 8.7 metres in width, rising to a modest 0.8 metres in height, with an opening 5.4 metres wide facing north-west. It was first recorded by Bowman in 1934. The site sits roughly 20 metres east of the river, which would have supplied the water essential to its operation. What makes its position in Ummeraboy especially interesting is that a second fulacht fiadh lies approximately 200 metres to the north-east, suggesting that this stretch of marshy ground beside the Athnaloingebaine was a place people returned to, and perhaps organised activity around, over a considerable period of prehistoric time.