The 1915 Ordnance Survey six-inch map labels it 'Cahernagrian', yet the site correctly bearing that name sits roughly 135 metres away to the north-east. A cashel is a stone-walled ringfort, a type of enclosed settlement built across early medieval Ireland, and this particular example occupies level ground in a rocky Clare landscape, with partial sea views opening out from the west-south-west to the north and steep natural ledges rising behind it to the north-north-west and south-east.

The antiquarian Thomas Johnson Westropp visited and recorded the site twice in the early twentieth century, noting in 1900 that it was a fort in Ballynahown, and returning in 1905 to describe it more precisely as 'an over-thrown stone fort, wrongly called Cahernagrian'. His measurements put the diameter at around 30 metres, and he observed that the collapsed walls, constructed from large blocks and what he considered good masonry, still stood between roughly one and one-and-a-quarter metres high and ran to widths of nearly two and a half metres. He also recorded hut-enclosures and additional internal walls within the cashel, suggesting a settlement of some complexity. The structure today is broadly circular, measuring approximately 30 metres east to west and 27 metres north to south. The outer wall-face survives only intermittently, though it is best preserved along the southern to north-eastern arc, where it still reaches up to one and a half metres in height. The internal features Westropp described are no longer distinguishable at ground level. A conjoined enclosure lies immediately to the south, and the site sits within a wider field system, hinting at a landscape that was once organised and inhabited rather than simply enclosed.