The rath at Drinaun is circular and measures roughly 31.5 metres in diameter, but the bank and external fosse that once defined it have largely vanished. A rath is a ringfort, typically an earthen enclosure built during the early medieval period in Ireland, most often as a farmstead for a family of some local status. At Drinaun, the defining features survive only in part: for more than half the circuit, from the west-south-west around through north to north-east, no surface trace remains at all.

Two forces account for much of the damage. A road cuts directly through the northern arc of the monument, removing what would have been a continuous earthwork and replacing it with tarmac and verge. From the north-east around to the east, a quarry has encroached upon the site, eating into the perimeter from that direction. What survives is a partial, interrupted outline of something that was once a coherent and functioning enclosure, probably farmed or settled during the early centuries of the first millennium. The fosse, a defensive or boundary ditch dug outside the bank, is no longer visible in these affected sections, and it is only in the remaining arcs of the circuit that the original form of the monument can be inferred at all.