At Belderny in County Galway, a circular earthwork roughly thirty metres in diameter once sat in level grassland, substantial enough to be recorded on the first edition of the Ordnance Survey six-inch map compiled in the nineteenth century. Today, nothing of it can be seen at ground level. No bank, no ditch, no rise or hollow to betray that anything was ever there.

The first edition OS six-inch maps, surveyed across Ireland from the 1830s onwards, caught the landscape at a particular moment, when many early earthworks were still legible in the fields even if already degraded. A circular enclosure of this kind, around thirty metres across, would broadly fit the profile of a ringfort, the commonplace defended farmstead of early medieval Ireland, thousands of which once dotted the countryside. Whether Belderny's enclosure was of that type, or something older or more specialised, is not recorded. What the map preserved was simply the outline, and that outline is now the only evidence that the feature existed at all. Subsequent agriculture, drainage, or simple weathering erased whatever surface relief remained in the intervening century and a half.