Someone, at some point, quarried out the interior almost completely, cutting a two-metre access gap through the enclosing bank and filling in the fosse to get machinery or carts in and out. The result is an earthwork that reads, from a distance, as a coherent and well-preserved example of its type, but reveals itself on closer inspection as essentially hollow.

A rath, to use the Irish term for this category of monument, is a roughly circular enclosure defined by an earthen bank and ditch, typically dating from the early medieval period, roughly 500 to 1000 AD, and built as a defended farmstead. This one in Corbally sits on a low rise with open views across rolling grassland, and its outer dimensions are still clearly legible: approximately 38 metres north to south and 36 metres east to west, enclosed by a scarp that rises to 1.7 metres at the south-southeast. Outside the central bank runs a fosse, a defensive ditch about three metres wide, which is well preserved along much of its arc but fades to a shallow depression elsewhere. Beyond that, at the south and southeast, remnants of an external bank survive, stones still protruding from its outer slope. The western arc of the monument has been absorbed into the modern townland boundary, and a stretch of hedgerow and hawthorn along that side appears to follow the original curve of the rath quite faithfully.

The quarry pit that dominates the interior measures roughly 15 metres by 20 metres, extending almost the full east-to-west width of the enclosure, with its deepest section pressed against the western scarp. Aerial photography once prompted speculation about a souterrain beneath the surface, a souterrain being an underground stone-lined passage sometimes found in association with ringforts and thought to have served for storage or refuge. The linear features visible from the air are now considered more likely to be traces of the quarrying itself. Livestock have worn down portions of the scarp, and hawthorn has colonised the boundary to the west. A second rath lies roughly 200 metres to the north-northwest, close enough to suggest that this part of Corbally was once a relatively settled and organised early medieval landscape.