What looks at first like a natural undulation is in fact a rath, a type of ringfort common across early medieval Ireland, typically built between roughly 500 and 1000 AD as an enclosed farmstead for a single family or small community. This particular example at Corkagh Beg is modest but legible, a subcircular raised area measuring just over thirty metres at its longest axis, its edges defined by an earthen and stone bank.

The enclosing bank is broad, running to about five metres in width, though it sits quite low for much of its circuit, rising only a few centimetres to half a metre above the interior surface. Where the bank gives way, on the north-northwest to east-southeast arc and at the west-southwest, the boundary becomes a scarp instead, a steeper natural or cut slope that drops away more sharply, reaching nearly two and a half metres in height at its most pronounced. There is no fosse, the external ditch that often accompanies such enclosures elsewhere. A modern entrance gap on the northwest side, about four metres wide, may well follow the line of the original opening into the enclosure, though the earthwork itself offers no firm evidence either way.