That persistence of a family name attached to an earthwork many centuries older is itself worth pausing over. The monument is subcircular in plan, measuring roughly 37 metres north to south and 33 metres east to west, and it is more complex than a casual glance might suggest. Two stone-faced banks enclose the interior, with a fosse, a defensive ditch, running between them, and traces of a further scarp survive along the southern arc outside the outer bank.

Ringforts were the most common form of enclosed settlement in early medieval Ireland, typically dated to between the sixth and tenth centuries, though many were built earlier or later. Most were the farmsteads of relatively prosperous families, the enclosing banks and ditches serving as much to define status and contain livestock as to provide serious military defence. What makes Hernon's Rath particularly interesting is the concentration of features within and around it. Inside the enclosure there is a souterrain, an underground stone-lined passage or chamber that was used for storage and possibly as a place of refuge, and a corndryer or burnt mound feature of some kind. Pressed against the outer bank on the western side is a small grassed-over circular structure about four and a half metres across, tentatively identified as a house. A two-metre gap on the south-south-west side of the enclosure may represent the original entrance.

The monument has not escaped entirely intact. Several field boundaries cut across it, a common fate for earthworks that remained in agricultural landscapes long after their original purpose was forgotten. Even so, it retains enough of its original form, and enough of its internal complexity, to give a clear sense of what an early medieval enclosed farmstead actually looked like on the ground.