The enclosure measures around 27 metres across, and what survives is a raised interior platform defined by an earthen bank and an outer fosse, the fosse being the defensive ditch that typically accompanied such structures. On the northern side, the bank rises nearly 2.7 metres above the base of the ditch, which gives a sense of how imposing the boundary would once have appeared to anyone approaching from outside.

This is a rath, a type of enclosed settlement common across early medieval Ireland, generally dating from roughly the sixth to the twelfth century. Raths, sometimes also called ring forts, were typically the farmsteads of free farming families, their earthen banks serving as much to define status and contain livestock as to provide serious military defence. The Legnacreeve example follows the form closely: a roughly circular raised area, a substantial bank with a measurable internal and external height, and a fosse beyond that. The entrance lies to the east, where both the causeway across the fosse and the gap through the bank are noticeably widened, suggesting a deliberate and considered design for access. A further outer field bank survives to the south-west and west-north-west, hinting at the organised landscape that once surrounded the core enclosure. Notably, a second rath sits approximately 100 metres to the south-south-east, and paired or clustered raths of this kind are not unusual in Monaghan, a county whose drumlin topography made elevated enclosure sites naturally attractive to early settlers.

The drumlin setting is itself worth pausing over. Drumlins, the low elongated hills formed by glacial deposition that give much of south Ulster its distinctive egg-box landscape, offered early communities natural vantage points, drainage, and a degree of separation from the surrounding terrain. Siting an enclosure on a drumlin summit was a practical choice, and the Legnacreeve fort makes full use of the elevation, its bank heights amplified by the natural rise of the hill beneath them.