A cashel is a type of ringfort defined by a stone enclosure wall rather than an earthen bank, and this one is substantial: roughly oval in plan, measuring about 46 metres on its longest axis, with a double-faced wall averaging a metre in height on the exterior and reaching as much as 2.7 metres at its north-east arc. When the antiquarian T. J. Westropp visited in 1896 he recorded the wall standing up to 3 metres high and wide in places, and he noted the deliberate use of massive header blocks, some of them over two metres long, worked into the fabric. Much of that original outer face still survives, built in part directly onto sheets of exposed limestone pavement, the wall's foundation and the wider landscape being, in a sense, the same material.

The site is recorded on Ordnance Survey maps going back to the 1897 twenty-five-inch edition under the name Mohernacartan, and appears as Mothair na Ceartán on Tim Robinson's map of the Burren from 1977. The Irish name carries a particular resonance: local folkloric tradition, recorded as far back as 1839 in the Ordnance Survey Letters, connects the enclosure with Garraidh na Ceártan, a field associated with Lon Mac Loimhtha, the mythological smith of the Tuatha Dé Danann, the supernatural race of pre-Christian Irish tradition. Westropp, who was alert to such survivals, pursued the connection further in a paper on the Cow Legend of Corofin published in the Journal of the Royal Society of Antiquaries of Ireland in 1895. Inside the cashel there is also a souterrain, an underground stone-lined passage or chamber of the kind commonly found within early medieval enclosures, situated in the north-north-west sector of the otherwise level interior. A second gap in the wall at the east-north-east, with scattered stones tumbling down the slope outside it, suggests either a secondary entrance or a later breach, and a short internal wall running inward from its edge complicates the picture further. Several later field walls radiate outward from the cashel, one of which, heading north, may itself be ancient and related to the original entrance.