The enclosure measures roughly 32 metres north to south and 30 metres east to west, its interior worn into a shallow saucer shape, the kind of subtle depression that only makes sense once you understand what you are standing in. The defining feature is a scarp, an earthen bank or cut edge, rising to about 2.3 metres, which traces the boundary of what was once somebody's fortified homestead.

A rath is the Irish term for a ringfort, a roughly circular enclosure typically constructed during the early medieval period, between around the fifth and twelfth centuries. They were not primarily military installations but farmsteads, the enclosed living spaces of farmers and their families, the bank and ditch providing a degree of protection for people and livestock alike. At Clonmoyle, a shallow external fosse, a defensive ditch, survives for a short distance on the western side, though it reaches only about half a metre in depth. On the northern side, a break in the scarp that might once have served as an entrance is now blocked by a field boundary that runs tangentially to the enclosure, a later agricultural line cutting across and effectively sealing off whatever opening was once there. It is a small detail, but an instructive one: the landscape has been reorganised around this feature over the centuries, each era leaving its own layer on top of the last.