This is a fulacht fia, one of the most common yet least understood monument types in the Irish landscape. The term refers to a burnt mound, the debris left behind by a Bronze Age cooking method in which stones were repeatedly heated in fire and then dropped into a water-filled trough to bring the water to boiling point. The stones, cracked and shattered by the thermal shock, were discarded beside the trough and built up over generations into the low horseshoe or oval shapes still visible across the country today.

The Finnoo example sits immediately north of a natural water spring, which is typical of the type. Access to a reliable water source was essential to the whole process, and it is the proximity to springs, streams, and boggy ground that most often alerts archaeologists to a fulacht's presence. The mound here measures roughly 19 metres north to south and just under 15 metres east to west, with a circular depression near its centre, approximately 7.2 metres by 7.5 metres and dropping around 0.4 metres below the mound surface. That hollow almost certainly marks the position of the original trough. The site was recorded by Denis Power and uploaded to the national record in August 2011.

The ground around the mound is waterlogged and thick with rushes, which gives a reasonable sense of the wet, marginal environment these sites typically occupy. Anyone making their way out to look at it should be prepared for soft ground underfoot, particularly after rain. There is nothing dramatic to see from a distance; the mound is low and easy to overlook in rough pasture. What rewards attention is the logic of the place itself, the spring just to the south, the dark burnt stone compressed into the earth, and the faint hollow at the centre where, at some point in the Bronze Age, someone was regularly and industriously boiling water.