The enclosure measures roughly 33 metres north to south and 35 metres east to west, enclosed by an earthen bank that still stands to a height of 2.3 metres in places. Around much of its circuit, an external fosse, essentially a defensive ditch cut into the ground, accompanies the bank, reaching about a metre in depth along the north-west to east-north-east arc, though it becomes noticeably shallower elsewhere.

This is a rath, the most common type of early medieval settlement monument in Ireland. Raths were typically built between roughly the fifth and twelfth centuries as enclosed farmsteads, their earthen banks and ditches marking both a boundary and a degree of social status for the families who lived within them. At Cusovinna, the bank has been badly eroded on its western side, and there is a gap about two metres wide to the east-north-east, along with a short levelled section just south of that gap. These breaks may reflect later agricultural interference rather than any original entrance arrangement. Perhaps most telling of the site's later history are the cultivation ridges that run across the interior on an east to west axis, evidence that the enclosed area was at some point given over to tillage, most likely lazy beds of the kind associated with potato cultivation in the post-medieval period. The interior of a prehistoric or early medieval enclosure being pressed into agricultural service is not unusual in Cork, but it does leave the archaeology of the original occupation layers considerably harder to read.