What appears at first glance to be a slight irregularity in the ground resolves, on closer inspection, into the eroded remains of a rath, the Irish term for a roughly circular enclosure defined by one or more earthen banks and ditches, typically built to protect a single farming household and its livestock somewhere between the fifth and twelfth centuries. This one is imperfect in outline, neither quite round nor quite oval, measuring roughly 45 metres north to south and 41.5 metres east to west.

The enclosure consists of two banks with a fosse, or ditch, cut between them, a more substantial arrangement than the single-bank raths that are the most common survival of their type. Even so, the site is poorly preserved, its profile worn down over the centuries by the same agricultural activity that would once have made use of the land inside its banks. What makes the site particularly curious is a detail of modern administration intruding on ancient geography: the townland boundary, the invisible but legally significant line dividing Cartron from a neighbouring townland, cuts directly through the enclosing elements on the eastern side. The rath predates any such administrative division by many centuries, and the boundary line takes no notice of it, slicing across the earthworks as though they were not there.