Others have been so thoroughly flattened by the plough that the only evidence left is what a dry summer occasionally draws out of the soil. The rath at Ballydonfin, in County Wexford, belongs firmly to the second category, surviving not as a landscape feature but as a ghost, visible only from the air under the right conditions.

What the aerial photographs reveal is a cropmark, roughly 35 metres in diameter, tracing the outline of a circular enclosure defined by a single fosse, the term for the ditch that would originally have bounded a rath or ringfort. In early medieval Ireland, ringforts served as enclosed farmsteads, with the surrounding bank and ditch providing security for a family and their livestock. At Ballydonfin the enclosure sits in the fold of a small stream running roughly northwest to southeast, with the watercourse itself lying about 40 metres to the northeast, a detail that fits a familiar pattern of early settlement close to reliable water. The cropmark is faint enough to be described as slight, meaning the underlying fosse has been reduced almost entirely, its presence betrayed only by the differential growth of crops above the filled-in ditch. Aerial photography taken in 2004 captured the clearest documentation of it.