What survives is only partial, and easy to walk past without recognising it for what it is: the remains of an oval rath, a type of enclosed farmstead that was once among the most common features of the Irish rural landscape.

A rath, broadly speaking, was a circular or near-circular enclosure defined by one or more earthen banks and ditches, used as a defended homestead during the early medieval period. Tens of thousands once existed across Ireland, though many have been lost to agriculture, development, or simple erosion over the centuries. This one in Crumlin measures roughly 60.5 metres north to south and 52.6 metres east to west, making it a reasonably substantial example, though what remains is poorly preserved. A field wall, almost certainly a later addition to the landscape, cuts directly through the monument at the north-north-east and again to the west. To the north-west, the enclosing bank has vanished entirely from the surface, leaving only the surviving arc to suggest the full shape of what was once here. It is a common fate for monuments of this kind, where generations of farmers, working without any knowledge of what lay beneath their feet, inadvertently dismantled earthworks that had stood for centuries.