Somewhere beneath the fields of Walterstown, Co. Kildare, lies the ghost of an enclosure that has never been excavated, never been mapped on the ground, and may never have drawn any serious attention at all. It exists, for now, only as a cropmark, a phenomenon where buried features beneath the surface cause overlying crops or grass to grow at slightly different rates, producing faint outlines that become legible only from the air under the right conditions of drought and low sun. What appeared in aerial imagery captured on 28 June 2018 was a roughly oval ring, approximately 50 metres across on its north-east to south-west axis and 45 metres on its north-west to south-east axis, sitting quietly in agricultural land with no surface trace whatsoever.

Enclosures of this kind are common across Ireland, though their individual histories vary considerably. Depending on date and function, a circular enclosure of this size might represent a ringfort, the remains of a farmstead from the early medieval period, or something considerably older. Without excavation, it is impossible to say which applies here. What the cropmark does confirm is that something was constructed or dug into the ground at this spot, and that its outline has survived, invisible but intact, long enough to be caught by a satellite camera on a summer afternoon.