What makes it quietly unusual is the density of what survives within its walls: not just the enclosure itself, but the footprints of five separate houses and an underground passage, all contained within an interior measuring roughly 35 metres east to west and 20 metres north to south.

This is a cashel, a type of ringfort defined by stone walls rather than earthen banks, and the Barnaderg example was originally defended by two concentric walls with a fosse, or ditch, running between them. That outer ring of defence has largely disappeared at the southern side, where neither the fosse nor the outer wall leaves any trace on the ground. Elsewhere, a later field wall has been built directly over the outer wall between the north-west and north-north-east, which is itself a small piece of agricultural history pressed into the archaeology. The southern gap in the inner wall, at just under three metres wide, may be the original entrance. Inside, alongside the remains of the five houses, there is a souterrain, an underground stone-lined passage or chamber of the kind commonly built during the early medieval period in Ireland, used variously for storage, refuge, or as a means of concealed escape.

The site sits on a knoll, so the enclosure would have had a natural elevation above the surrounding land, a modest but meaningful advantage for anyone living within it. The combination of the double-walled cashel, the internal houses, and the souterrain suggests a settlement of some complexity, the kind of enclosed farmstead that a person of local standing might have occupied during the early medieval centuries. The partial survival of so many internal features in one place makes it more legible than many comparable sites where the interior has been cleared or ploughed flat.