At Knockboy in County Waterford, a small circular enclosure roughly thirty metres across sits in ordinary pasture on level ground, doing nothing to announce itself. It cannot be seen from the surface at all. The only reason anyone knows it is there is that the Ordnance Survey recorded it on their six-inch map in 1840, tracing a circle that has since been quietly swallowed by grass and time.

Circular enclosures of this kind are among the more common, if poorly understood, features of the Irish archaeological landscape. They may represent the ditched or embanked boundaries of early medieval farmsteads, known as ringforts, or they may be earlier still, associated with prehistoric settlement or ritual use of the land. Without excavation it is rarely possible to say which. What is notable about the Knockboy example is how completely it has vanished from view, leaving only its cartographic ghost on a nineteenth-century map as evidence that something was once deliberately marked out here. The surveyors who walked this ground in the 1830s and 1840s were meticulous recorders of earthworks and field boundaries, and their decision to note this feature suggests it was at least faintly legible in their day, even if it is not in ours.