At Marybrook in north County Cork, a prehistoric or early medieval fort once occupied the edge of a steep scarp dropping away to the south, a position typical of defended enclosures that used natural drops in the landscape as part of their fortification. Today there is nothing to see at ground level. The field fence that once marked part of the site has been levelled, and the surrounding land is under tillage. The fort exists now only as a cropmark, that faint discolouration in growing crops caused by buried features affecting soil moisture and plant growth, visible in an aerial photograph taken in July 1989 as part of the Cork Aerial Survey and Photography project. The image shows the arc of a fosse, the external ditch that would have ringed the enclosure, running from the south-west to the east-south-east along the northern side of a former field boundary.

The site may have a paper trail of sorts, though a thin one. A 1934 account by Bowman recorded a number of levelled forts in this area, among them one situated in a field known locally as "pairc a daingin", an Irish phrase meaning roughly "the fort field", on land then belonging to a Mr Cronin. The coincidence of location and the telling placename suggest this may be the same site, one that local memory had already half-preserved in the name of the field long after the earthwork itself had disappeared. Placenames of this kind are a recurring feature of the Irish landscape, often outlasting by centuries the physical remains they once described.