What makes this one unusual is not merely its survival but its layered complexity: three concentric lines of defence, a substantial stone wall built against the inner bank face, and the remnants of a small oval hut still tucked against that inner wall. Most ringforts, which were the enclosed farmsteads of early medieval Ireland, typically present a single bank and fosse. This one went considerably further.

A ringfort, or rath, was the standard unit of rural settlement in Ireland roughly between the fifth and twelfth centuries, a circular enclosure defined by one or more earthen banks and ditches, fosse being the term for that outer ditch, intended to provide security for a farming household and its livestock. At Caherbarnagh the outer bank still stands 4.1 metres high, with the remains of a stone wall, now partially collapsed, rising a further 1.6 metres against its inner face. The stepped inner face of that wall survives most clearly to the south-west. Two further banks of earth and stone complete the enclosure on the outer circuit, though to the south-west and west-north-west these have been absorbed into later dry-stone field boundaries, the kind of quiet recycling of ancient structures that was commonplace as agricultural land was reorganised in subsequent centuries. Entry was made through a causewayed gap to the north, a raised approach across the fosse rather than a bridge. Inside, the ground slopes downward toward that same northern entrance, and against the western inner wall the remains of a small oval structure survive, its dry-stone walls still standing to nearly a metre, with traces of inward corbelling at the top, suggesting a beehive-style roofing technique that was common in early Irish construction.