A rath, or ringfort, is a roughly circular enclosure defined by an earthen bank and ditch, built during the early medieval period and used as a farmstead or place of shelter. Here, that familiar form survives only just, the enclosure measuring approximately 36 metres north to south and 32 metres east to west, its edges legible mainly as a low scarp and an external fosse, a shallow defensive ditch, running from the south around through the west to the north. On the remaining arc, a slight rise in the ground is all that marks the boundary.

The site sits in undulating grassland that looks out over bogland to the south, a landscape that would have been a working resource in early medieval times, providing fuel, grazing, and a degree of natural protection. What has done the most visible damage to the monument, though, is not age or boggy ground but something more mundane: a field wall has been driven straight through the earthwork at both the northern and southern points, cutting across the rath in the way that centuries of agricultural reorganisation so often do. A related enclosure lies roughly 300 metres to the west-northwest, suggesting this part of Cloonnacross once held a small cluster of such features, though what relationship they had to one another is not recorded. The site was noted by researchers around 1975 and 1980, by which point its poor condition was already a defining characteristic.