At Kilmartin in County Cork, there is a ringfort, or rath, that exists now only as a cartographic memory, recorded on the Ordnance Survey's six-inch map of 1842 as a hachured circle, the surveyors' convention for showing an earthwork rising from the ground. Today, there is no visible surface trace at all.

The enclosure, roughly twenty metres in diameter, was a rath, the most common type of early medieval settlement monument in Ireland. These were typically circular earthen banks enclosing a domestic space, used by farming families somewhere between the sixth and twelfth centuries. The Kilmartin example was modest by any measure, its diameter placing it at the smaller end of the scale. By the time anyone thought to record it formally, the levelling was already complete. The 1842 map caught it at, or just before, the point of erasure, making that early Ordnance Survey sheet the sole evidence that it was ever there.