This is a fulacht fia, a type of prehistoric cooking site found across Ireland in considerable numbers, typically dating to the Bronze Age. The standard interpretation is that water was heated in a trough by dropping fire-cracked stones into it, and over time the discarded burnt stone accumulated into the characteristic horseshoe or circular mound that survives today. What makes the Cloonfinglas example quietly notable is that it is not alone: a second fulacht fia lies roughly thirty metres to the north-north-west, suggesting this gentle south-west-facing slope saw repeated or sustained use in prehistory.

The site was first identified by M. A. Timoney, and the mound measures approximately 11.9 metres across on its north-east to south-west axis and 10.9 metres on the north-west to south-east axis, rising only 0.3 to 0.4 metres above the surrounding ground. A small depression, roughly two metres by one metre, sits on the perimeter at the north-west edge, which may mark the location of the original trough or a later disturbance. At these modest dimensions and height, the mound is easy to overlook, which is perhaps why it escaped notice until relatively recently. The grass-covered burnt stone gives it the appearance of a natural feature rather than anything made by human hands.