It measures roughly 16.7 metres long, 11.5 metres wide, and rises about a metre from the surrounding pasture, with a two-metre opening facing north. To most eyes it would read as an unremarkable rise in the ground. What it actually represents is one of the most common prehistoric monument types in Ireland, and one of the least understood.

A fulacht fia, sometimes called a burnt mound, is the remains of an ancient cooking or heating site, typically Bronze Age in date. The characteristic kidney or horseshoe shape comes from the gradual accumulation of fire-cracked stones, discarded after being heated and plunged into a water-filled trough to bring it to the boil. Tens of thousands of these sites have been recorded across Ireland, often positioned close to streams or boggy ground where water was readily available, exactly the kind of setting this example occupies. What is slightly unusual about Coolageela is that a second fulacht fia lies roughly 200 metres to the south-west, raising the question of whether the two sites were in use at the same time, by the same community, or whether one succeeded the other across generations. The notes offer no answer, and archaeology rarely does.