That truncation is one of the more jarring details about the cashel known as Cathair Bhearnach, a roughly circular stone ringfort in County Clare sitting amid rough pasture and the exposed, fissured limestone typical of the Burren's karstic landscape, where the rock seems to push through the surface like something impatient to be seen.

A cashel is a ringfort built primarily from stone rather than earthen banks, and this one measures approximately 36 metres east to west and 34 metres north to south. The scholar T. J. Westropp translated the name in 1901 as 'stone fort of the gap', a description that still holds given the 2-metre entrance gap that survives on the eastern side. The enclosing bank is a round-topped construction of earth and stone, and traces of upright limestone slab revetting survive on both faces, suggesting it was once carefully faced on the inside and outside alike. Beyond the bank, a berm and an outer scarp survive from the south-west around to the east, and south of the entrance there is a fosse, a defensive ditch, accompanied by its own outer bank, the two together spanning up to 8 metres in width. The site appears on the Ordnance Survey six-inch maps of 1842 and 1920, and was also marked on Tim Robinson's 1977 map of the area, so its presence in the local landscape has been recognised for well over a century.

The interior holds several structural puzzles. Against the north-western bank-face sits a subtriangular platform in two levels, the upper rising to about 0.8 metres. At the south-east, another triangular area is defined by a low, grass-covered collapsed wall. In the northern sector, a roughly rectangular enclosure is bounded on its western side by a collapsed stone wall and along its southern edge by a line of upright limestone slabs; a few further uprights to the west hint at a second similar enclosure nearby. Aerial imagery has also revealed a rectangular feature at the south-west, roughly 11 metres by 7 metres. The site sits within a wider multiperiod field system, so what looks like an isolated fort is, in fact, one layer of a much longer story of people organising and working this limestone ground.