It measures roughly 19 metres east to west and 16 metres north to south, and to an untrained eye it might pass for a slight irregularity in the ground. It is, however, a fulacht fia, one of the most common yet least-understood monument types in the Irish archaeological landscape.

Fulachtaí fia are prehistoric cooking sites, found in their thousands across Ireland, typically dating from the Bronze Age. The usual interpretation is that a trough was dug into the ground and lined, water was channelled or collected into it, and stones heated in a nearby fire were then dropped into the water to bring it to a boil. The burnt and shattered stones, discarded after use, gradually accumulated into the characteristic horseshoe-shaped or oval mound that survives today. The presence of natural springs at Baurnahulla would have made the site well suited to this kind of activity, providing a reliable water source close at hand. Some researchers have questioned whether cooking was the only, or even the primary, function of such sites, with proposals ranging from textile processing to bathing, though no consensus has settled the debate.