The place is called Dún Beag, a name meaning small fort in Irish, and the decision to build here was clearly defensive in logic: the steep falls from ENE to SW make the site naturally formidable without requiring elaborate earthworks on those exposed flanks.

What survives is a cashel, a type of ringfort enclosed by a dry-stone wall rather than an earthen bank, and this one is in poor condition. The original wall was between 2.2 and 3 metres wide and built with two stone faces, but it has tumbled and been rebuilt in places over the centuries. The interior, which measures roughly 28 metres across, sits about 1.8 metres lower than the surrounding ground to the north and north-east, a consequence of the bedrock having been partially quarried and terraced to level the floor. At the north-east corner, a natural bluff takes over from the wall entirely, with only faint traces of inner stone-facing surviving near its base. There is no obvious original entrance, though the most accessible approach runs along a terrace to the north, which is the most plausible location for one. The site was recorded on Ordnance Survey six-inch maps in both 1842 and 1915 under the name Coskeam fort. Inside, two subcircular house sites sit near the centre, the footprints of small round structures whose occupants remain unknown, and a nearby cairn may conceal a third. Against the inner face of the wall in the north-west sector, a small drystone animal shelter, roughly three metres square, was added at some later date, someone finding a practical use for walls that were already centuries old.