The structure at Cloonyquin is a roughly circular embanked enclosure, its interior measuring about 28 to 29 metres across, defined by the remains of a wall some two and a half metres wide. What survives today is a scarp, essentially a stepped or sloping edge where the ground drops away, ranging from around 30 centimetres high on the western side to as much as 1.4 metres on the southern. Where the scarp fades, the steep natural slope of the hillock takes over, suggesting the original builders knew how to let the topography do some of the work. A possible entrance was identified at the south-east.

Outside the scarp, a band of reeds roughly four to five metres wide traces the perimeter. Reeds tend to establish themselves in wet or waterlogged ground, and here they almost certainly mark the line of a fosse, a ditch dug to define and defend the enclosure's outer edge. The combination of a raised interior, a surrounding wall, and an outer ditch places this within a tradition of enclosed hilltop sites found across early medieval Ireland, though the site has not been closely dated. It does not sit in isolation. A cashel, a stone-walled enclosure of the kind typically associated with early medieval settlement, lies about 150 metres to the south, and two cairns, mounds of stones often associated with prehistoric burial, sit nearby to the east and east-north-east. Together they suggest this particular hillock was a focus of activity across more than one period.