At Knockilly in County Cork, a west-facing pasture slope holds the remains of an enclosure that has left no visible mark on the ground whatsoever. It survives only as a cartographic ghost, drawn onto the Ordnance Survey six-inch map of 1842 as a hachured circle, the conventional symbol surveyors used to indicate a raised or embanked circular feature, roughly fifteen metres across. Whatever once defined it on the ground, bank or ditch or both, has long since been levelled into the surrounding grassland.

The site may be the same structure recorded in 1934 by a researcher named Bowman, who noted a fort on Patrick O'Connor's land that had already been levelled by that point. Bowman described it as rectangular in plan, measuring thirteen yards by sixteen, which sits awkwardly against the circular depiction on the earlier OS map. Whether the two accounts refer to the same feature or to different phases of the same enclosure is unclear. What adds genuine interest is a separate but related find: Bowman recorded a souterrain, an underground stone-lined passage of the kind commonly associated with early medieval settlements in Ireland, located about twenty yards to the west of the fort. Souterrains were typically used for storage or as places of refuge, and their presence close to an enclosure of this kind is a fairly reliable indicator that the site was once a functioning farmstead, probably dating to the early medieval period.