What was once a defined enclosure is now little more than a series of faint earthworks, easily mistaken for the ordinary undulations of a field. The outer bank survives only along the southern and western arc, running round to the northwest before fading entirely, and the intervening fosse, the shallow ditch that once separated the bank from the main enclosure, is similarly worn down to a gentle depression. It is the kind of site that rewards careful attention rather than a casual glance.

A rath is a ringfort, the most common monument type in the Irish landscape, typically a roughly circular area enclosed by one or more earthen banks and ditches. They date broadly to the early medieval period, roughly the sixth to tenth centuries, and are generally interpreted as farmsteads, the defended homesteads of farming families rather than military fortifications in any grand sense. This example at Knockogonnell is subcircular in plan, measuring approximately 48 metres on its northeast to southwest axis and 44 metres northwest to southeast, dimensions that place it comfortably within the typical range for such enclosures. The degraded scarp that now defines much of the perimeter suggests the original bank has slumped and spread over centuries of agricultural use, the gradual consequence of ploughing, grazing, and the general indifference of working land to ancient boundaries.