This is a cashel, a type of ringfort built from stone rather than the earthen banks more commonly associated with early medieval settlement in Ireland. Where a typical earthwork ringfort relies on ditched ramparts, a cashel uses a mortarless stone wall to define its boundary, and the one at Kilnacranagh still stands to a height of around 1.7 metres across much of its circuit.

The enclosure measures roughly 49 metres north to south and 42.7 metres east to west, giving it a slightly elongated oval plan. The wall itself shows some variation in its construction: the lower courses along the northern and north-eastern stretches incorporate large flat slabs, suggesting either a deliberate structural choice or the reuse of earlier material. A gap roughly 2 metres wide in the north-western section of the wall marks what was likely the original entrance, the point through which people, animals, and goods would have passed during the site's period of use. Inside the enclosure, a natural rock outcrop breaks the surface, a reminder that the builders chose this elevated ground in part because bedrock was close at hand, both as a foundation and as a practical source of building stone. Cashels of this kind are generally associated with the early medieval period in Ireland, roughly the fifth to twelfth centuries, when enclosed farmsteads were the dominant form of rural settlement across the island.