The monument is oval in plan, with a level interior measuring roughly 36 metres north to south and 24 metres east to west, enclosed by a deep fosse, a sheer inner bank dropping over four metres on the eastern side, and a considerable outer bank built up with a notable quantity of stone. A causewayed entrance, the kind of deliberately raised crossing left over a defensive ditch, survives at the west-southwest. The scale and engineering are serious: this is not a casual accumulation of earth.

The site carries two quite different identities, separated by many centuries. Writing in 1905, the historian Canon Carrigan recorded a tradition, drawn from earlier Irish annalists, that the earthwork was raised by Heremon, son of Milesius, one of the mythological kings said to have ruled Ireland in the remote prehistoric past. According to that same tradition, Heremon also chose the site as his burial place. Whether or not any such figure existed, the association points to the monument's evident antiquity and local significance in the medieval imagination. The physical evidence, however, tells a somewhat different story. The combination of a high interior platform, a deep fosse, a strong outer bank, and a causewayed entrance is characteristic of an Anglo-Norman ringwork, a type of defended enclosure built by Norman lords after the invasion of the late twelfth century, typically as a fortified residence rather than a purely military structure. The two interpretations are not necessarily incompatible; Anglo-Norman builders sometimes chose existing earthworks and earlier sacred sites for their own constructions, layering new authority over older ground.