Somewhere in the townland of Castletown in County Waterford, a circular enclosure between thirty-five and forty metres across sits on a gentle east-facing slope, invisible to anyone standing beside it. No earthwork rises above the surrounding ground; no obvious ditch or bank signals its presence. It exists, for the practical purposes of a visitor, only on paper.

The enclosure was recorded on the Ordnance Survey six-inch maps of 1840 and again on the 1950 to 1951 edition, suggesting that whatever feature was once legible in the landscape had already begun to fade well before the twentieth century. Circular enclosures of this kind are among the most common archaeological forms in Ireland, ranging from prehistoric ring-ditches to the ringforts, known in Irish as ráth or lios, that were used as enclosed farmsteads during the early medieval period. Their circularity is usually the first thing that betrays them on a map, even when ploughing, quarrying, or overgrowth has long since erased the physical relief. At Castletown, the combination of all three seems to have done its work thoroughly. The area is noted as overgrown and partially quarried, which accounts both for the invisibility at ground level and for the likelihood that whatever remained of the original bank or ditch has been further disturbed since those mid-century map editions were drawn.