A rath, or ringfort, is a roughly circular enclosure defined by an earthen bank and, typically, an external ditch or fosse; they were built in their thousands across Ireland during the early medieval period, serving as farmsteads and enclosures for livestock. This one in Ballyduagh measures approximately 26 metres east to west and 24 metres north to south, with a bank that, where it survives best, rises about 1.25 metres above the surrounding ground on its outer face, though in places it has been worn down to little more than a low scarp.

What makes the site quietly interesting is a small contradiction in its recorded history. A sketch plan and profiles produced from Ordnance Survey field work in 1954 recorded a fosse running along the north-western to north-eastern arc of the monument. Yet a survey conducted by Cahill in 1982 found no evidence of a ditch at all, describing the site simply as a high, raised area enclosed by a bank. Whether the fosse was filled in during the intervening decades, or whether it was always ambiguous on the ground, the two accounts do not quite agree. The interior of the enclosure is dish-shaped, which is a common characteristic of these sites, and a 3-metre entrance gap at the south-east is thought to be a modern intrusion rather than an original feature.