The enclosure measures around 23 metres in diameter, and what remains of its defining bank has slumped over time into a low scarp, surviving to about a metre in height at its southern side. A fosse, the term for the external ditch that typically accompanied such earthen enclosures, still traces the perimeter, though it has been absorbed into a field drain running from west to north-east. Someone has cut a modern entrance at the south-east, but wherever people once actually walked in and out, that original gap has not been identified.

Drumlin country shapes everything about this part of Monaghan. The landscape is a legacy of the last glaciation, a rolling terrain of egg-shaped hills deposited by retreating ice, and these modest elevations were frequently chosen for enclosures of this kind. Earthen ringforts, known in Irish as raths, were the most common form of defended farmstead in early medieval Ireland, typically dating from roughly the sixth to the twelfth centuries, though some are older. They generally consisted of a circular bank and fosse enclosing a domestic area, and the bank at Mullaghcor, even in its diminished state, follows that familiar grammar. The slight elevation of the drumlin would have offered reasonable visibility across the surrounding terrain, which was likely as much about social signalling as it was about any serious defensive need.