Below, the valley of the Bride river drops away sharply, and it is this cliff face that forms one entire side of an early fort, doing the work that a rampart would otherwise have to do. The arrangement is quietly ingenious, and it gives the enclosure its slightly asymmetrical character.

The fort is D-shaped in plan, measuring roughly 32 metres north to south and 37 metres east to west. Three sides are defined by an earthen scarp, a stepped or sloped bank cut and piled from the surrounding ground, standing about two metres high, with a very shallow fosse, or ditch, running along its outer edge. The southern side dispenses with all of that entirely, relying instead on the natural drama of the cliff. This kind of promontory or cliff-edge enclosure was a practical solution used at various points throughout Irish prehistory and the early medieval period, the builders reading the landscape and incorporating its most defensible features rather than replicating them artificially. The interior of this example is level, which suggests it was deliberately levelled at some point, though it is now overgrown with pasture vegetation.