Where most ringforts, the circular enclosures built by early medieval Irish farming families for settlement and protection, rely entirely on their own construction to define a perimeter, this one simply stops at the cliff. The natural drop to the east does the work that an earthen bank would otherwise have to do, and the result is a structure that is, in the technical sense, penannular, a ring left deliberately open because the landscape itself closes it.

The enclosure measures roughly 32 metres north-northeast to south-southwest, and 30 metres in the perpendicular direction before the cliff edge takes over. The surviving earthen bank rises to an internal height of around 1.9 metres and an external height of 2.3 metres, with a shallow fosse, a defensive ditch, cut into the ground to the north-northeast. The bank is at its most substantial to the northwest and tapers as it approaches the cliff on both sides, suggesting the builders shaped it with the natural boundary firmly in mind. By 1842, when the first Ordnance Survey six-inch maps recorded the area, the enclosure was already being drawn as a circular form; later surveys in 1905 and 1934 show a penannular outline with a straight fence abutting it to the east, by which point the field boundaries of a much later agricultural era had begun to press against the older earthwork. The interior slopes gently downward toward the southeast and today serves as grazing pasture. From within, Ballyderown Castle is visible to the southwest, a reminder that this elevated ground above the Araglin River held strategic value across very different periods of Irish history.