A low circular platform, roughly 37 metres across and barely a metre high, sits on a break in an east-facing slope, the ground around it given over to pasture. The earthwork has been levelled, its original banks spread or ploughed away, but the scarped edge of that platform persists, tracing the ghost of an enclosure that was once a functioning farmstead.

A ringfort, sometimes called a rath, was the standard form of rural settlement in early medieval Ireland, typically consisting of a circular area enclosed by one or more earthen banks and ditches, used to shelter a farming household and its livestock. At Lisnabrin, the 1842 Ordnance Survey six-inch map recorded the site as a hachured circular enclosure, the cartographers' way of indicating an earthwork in the ground. By the time later editions of the same map series were drawn, the enclosure had been reduced to a curve in an east-west field fence, the monument absorbed so thoroughly into the agricultural boundary that only its outline remained legible. That cartographic sequence, from clearly marked earthwork to a kink in a field boundary, tells a quiet story of gradual erasure. Adding further texture to the site is its proximity to a companion monument: another ringfort and an associated souterrain sit around 80 metres to the north. A souterrain is an underground stone-lined passage, typically cut into the subsoil during the early medieval period and used for storage or, possibly, refuge. The clustering of two ringforts in close proximity is not unusual for Cork, where early medieval settlement could be dense, but it does suggest this particular slope was considered worth occupying by more than one community or household over time.