A ringfort, or rath, was a circular enclosed farmstead used throughout early medieval Ireland, typically defended by one or more earthen banks and ditches. What survives at Clooncullen is a subcircular platform, roughly 32 metres northwest to southeast and 29 metres north to south, edged by a low bank of earth and stone to the south and elsewhere by a gentle scarp, nowhere rising more than about half a metre above the surrounding ground. Scattered large boulders at the perimeter may be the remnants of a stone wall footing, though they now sit half-buried and easy to miss.

The site was already being described simply as a "Fort" on the Ordnance Survey's six-inch map of 1837, which suggests it was a recognised feature of the local landscape even then, if not a fully understood one. By 1976, there were still faint traces of an external fosse, the defensive ditch that would originally have enclosed the bank, but those traces have since disappeared entirely. The original entrance is no longer identifiable. What the 1837 cartographers recorded as a crisp circular enclosure is now a quiet irregularity in the pasture, its edges softened by the slow work of agriculture, weathering, and time.