The rath at Ardue is different. Here, the builders only needed to construct their bank and fosse, a ditch dug outside the bank, across part of the perimeter. Tomkinroad Lough did the rest, supplying a natural barrier along one side and giving the enclosure its distinctive D-shape rather than the more familiar round form.

The site measures roughly 72 metres on its longest axis and about 53 metres across. A substantial earthen bank runs from the south-east, around the west, and up to the north-north-east, where the lough takes over. A wide, shallow fosse runs outside the bank, and there are traces of what may be a counterscarp bank at the fosse's outer lip, an additional low ridge sometimes thrown up from the spoil of digging, which would have reinforced the defensive profile. An Office of Public Works inspection in 1974 suggested the original entrance was probably on the south-south-west side. The whole area is now densely overgrown, the vegetation having reclaimed whatever interior features may once have been visible above ground.