Drumlins, the smooth elongated hills left behind by retreating glaciers, are a defining feature of the Ulster landscape, and the people who built ringforts and enclosures in early medieval Ireland frequently chose their crests as natural platforms. What survives at Cordevlis is just enough to confirm something was once deliberately shaped here, and not quite enough to say much more.

The enclosure measures roughly 32.5 metres on its longer north-northwest to south-southeast axis, and around 25 metres across. A ringfort, or earthen enclosure of this kind, would typically have been defined by a bank and an outer ditch, known as a fosse, with a clear entrance. At Cordevlis, however, no fosse is visible, and no entrance has been identified. The surviving portion of the earthen bank runs along the south-east to west arc, where it still stands to an external height of around 2.5 metres and carries a width of approximately 4 metres; internally, it rises only about 1.1 metres above the enclosed ground. Elsewhere around the circuit, the bank has been largely removed, whether by agricultural clearance, the slow work of erosion, or both.