At Ballynidon in County Cork, on the northern side of a ridge, there once stood a ringfort roughly forty metres across, and the only reliable evidence that it existed at all comes from a map drawn in 1842. Today, there is no visible surface trace whatsoever.

Ringforts, also known as raths, were enclosed farmsteads typically built during the early medieval period, consisting of a circular area of raised ground surrounded by one or more earthen banks and ditches. They are among the most common archaeological monument types in Ireland, with tens of thousands recorded across the country. The Ballynidon example was captured by the Ordnance Survey's six-inch mapping programme, which systematically documented Ireland from the 1830s onward and inadvertently preserved a record of features that subsequent centuries of agriculture, land clearance, or simple erosion would erase entirely. Whatever once defined this enclosure, whether an earthen bank, a ditch, or both, has since levelled into the surrounding ground. A second possible ringfort lies approximately 220 metres to the east, suggesting this part of the ridge may have supported a small cluster of early medieval settlement, though that site too remains unconfirmed.