It is, in fact, a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, typically dating from the Bronze Age. The standard interpretation is that these sites were used for boiling water, achieved by heating stones in a fire and dropping them into a water-filled trough; the cracked and fire-shattered stones were then discarded into a mound nearby, which is what survives. This particular mound has a kidney shape, measuring 6.5 metres on its northeast to southwest axis and 3.4 metres across, rising only half a metre above the surrounding ground. An opening to the southeast, about 2.6 metres wide, marks where the trough or working area would once have been.

What makes the Dunbeacon example quietly interesting is not the mound itself so much as its immediate neighbour. A second fulacht fia lies just 22 metres to the west, close enough that the two sites were almost certainly in use by the same community, whether simultaneously or across successive generations. The proximity of a natural drain would have made the location practical; reliable water access was essential to the whole process. Together, the two mounds suggest a spot that was returned to repeatedly, a fixed point in a prehistoric landscape that has otherwise largely vanished.