This is a rath, the most common type of early medieval enclosure in Ireland, typically built between the sixth and tenth centuries as a fortified farmstead. The earthen bank would have defined both a domestic boundary and a social one, marking the household of a farmer of some standing within the tuatha, the local territorial unit of Gaelic Ireland. At Corbally, the enclosure measures roughly 29.5 metres on its longer axis and 27.4 metres across, making it a relatively modest example of the type.

By the time the Ordnance Survey recorded the area in 1837, the site was already reduced enough that the cartographers simply annotated it as "Fort" on their Fair Plan map. The 1913 revised OS 25-inch edition shows it more carefully, depicting the characteristic suboval outline of the earthwork. Descriptions from 1970 capture the monument in some detail: the bank survives best along the south-west, west, and north-north-east arc, where the exterior face remains steep, though the interior side has largely been reduced to a scarp. On the east, a gap in the bank, roughly 4.5 metres wide at the top and narrowing to 1.7 metres at its base, is accompanied by the remains of a ramp crossing the fosse, suggesting this was once a causewayed entrance, a deliberate bridge of earth left over the defensive ditch to allow access. By 1972, observers noted that the eastern and southern portions had been quarried away, damage which has left the surviving arc of bank looking more fragmentary on that side than on the better-preserved north and west.

The interior is not a flat, empty bowl. It rises gently toward the centre and is broken by humps, hollows, and occasional rock outcrop, the residue of whatever structures once stood within. The site sits on a slight rise with open views toward the north-north-west, a placement typical of ringforts, where a degree of visibility over the surrounding land was plainly valued. Two ESB electricity poles standing just outside the western bank serve as an inadvertent reminder of how completely the agricultural and infrastructural routines of later centuries have accumulated around these older features without entirely erasing them.