Roughly 29 metres across, it is the kind of feature that a passing walker might take for a natural rise, its defining bank now so grassed over and merged with a later field boundary to the south that its original outline takes some patience to read.

The structure is a ringfort, or the remains of one. Ringforts, also known as raths, are enclosed farmsteads typically dating from the early medieval period, roughly 500 to 1000 AD, and they survive in their thousands across Ireland, though many have been ploughed out or built over. This one in Clonacullan retains its earthen bank, which measures around 3.2 metres at the base and stands roughly 0.7 metres high on both its inner and outer faces. To the north-northwest and north-northeast, the bank is accompanied by an outer fosse, a shallow defensive or drainage ditch, though this too is largely filled and overgrown. On the eastern and southern sides, the bank has been worn down to a simple scarp, a slope in the ground rather than a raised feature, and at the south it has been folded into an ordinary field boundary, making it easy to overlook. No original entrance has been identified, which is common enough when vegetation and centuries of agricultural activity have reshaped the margins of a site like this.