A cashel is a stone-walled enclosure, the equivalent in drystone masonry of the more familiar earthen ringfort, and this one measures nearly 49 metres from north to south and 47 metres from east to west, its corners softened into rounded curves. When the antiquarian Thomas Johnson Westropp visited in 1896, he was not especially impressed, describing it as an angular enclosure defined by a poorly built, slight wall. That assessment remains largely fair. The southern wall, standing between 1.2 and 1.35 metres high and about a metre thick, is the best-preserved stretch, with recognisable outer facing surviving near its junction with the western wall. The northern and eastern walls have fared far worse, collapsing into low, shapeless stone spreads with no clear inner or outer facing remaining.

The site appears on the 1842 Ordnance Survey six-inch map under the name Knockan Fort, depicted as a subcircular hachured enclosure that virtually fills a small rectangular field. By the 1915 edition, only the field boundary was shown, the enclosure itself having become harder to read on the ground. Inside the eastern half, the same map shows the remains of a house and a souterrain, the latter being an underground stone-lined passage typically associated with early medieval settlement, used perhaps for storage or refuge. A second possible souterrain has since been identified closer to the centre of the interior, and the foundations of a hut site were noted in the north-east corner. Roughly 30 metres to the south-west lies a wedge tomb, a megalithic burial monument of a type common in the west of Ireland and generally dating to the later Neolithic or early Bronze Age, which suggests the broader landscape here was significant long before the cashel walls were raised.