There is an archaeological site at Kilnagrange, in County Waterford, that exists primarily as a cartographic ghost. A small oval enclosure, roughly thirty metres across its longer axis and twenty-five metres across its shorter, it was recorded on the Ordnance Survey's six-inch map of 1840 but has since vanished from view entirely. Stand on the broad ridge where it sits and you would see nothing unusual, just tillage land running across the high ground. The enclosure is not visible at ground level.

Embanked enclosures of this kind, defined by a low earthen bank forming a roughly circular or oval boundary, occur across Ireland and are associated with a range of periods and functions, from early medieval settlement to stock management to ritual use. The Kilnagrange example occupies a commanding position on a broad ridge aligned northeast to southwest, a placement that recalls the preference in earlier Irish archaeology for elevated, open ground. The fact that it was legible to the OS surveyors working in 1840 but has since been reduced to invisibility suggests that decades of agricultural activity on that tillage ground gradually levelled whatever earthwork remained. What the six-inch map captured was, in all likelihood, already a diminished version of an older feature.