A roughly circular raised platform, measuring approximately 32 metres east to west and 26 metres north to south, it sits defined by a scarp, a steep earthen edge, still standing around 1.4 metres high in places, with traces of an internal lip surviving around portions of the circuit. A shallow external fosse, essentially a ditch dug to complement the raised bank, runs around the outside, though at only around 0.2 metres deep it is considerably worn down from whatever it once was.

Ringforts, known in Irish as raths when they are earthen rather than stone-built, were the most common form of enclosed settlement in early medieval Ireland, typically dating from roughly the sixth to the twelfth centuries. They served as farmsteads for free farming families, the enclosing bank and ditch functioning less as military fortification and more as a boundary, keeping livestock in and wolves or opportunistic neighbours out. The Dunmahon example follows a familiar pattern, the interior sloping gently southward, which would have made drainage practical and the site reasonably comfortable for habitation or agricultural use. At some point, presumably in more recent times, the interior was planted with coniferous trees, which both obscures and, in a way, protects the underlying archaeology from the more disruptive effects of ploughing or heavy grazing.