Somewhere beneath the farmland at Nicholastown in County Kildare, a circular ditch lies buried and invisible at ground level, revealed only when viewed from the air under the right conditions. The feature is known from a single aerial photograph, in which it appears as a cropmark, a faint discolouration in growing vegetation caused by the way buried ditches retain moisture differently from the surrounding soil, producing subtle variations in crop colour and height that become legible only from altitude.

Ring-ditches of this kind are among the more enigmatic traces of prehistoric activity in the Irish landscape. They are typically circular or near-circular ditched enclosures, and many are thought to represent the ploughed-out remains of burial mounds, the earthen bank and central mound long since levelled by centuries of agriculture, leaving only the ditch as a shadow in the soil. Some may have functioned as ceremonial or funerary sites during the Bronze Age, though without excavation it is rarely possible to say more with confidence about any individual example. The Kildare lowlands, with their relatively flat, arable terrain, are particularly well suited to cropmark detection, and aerial survey has brought a number of such features to light across the county that would otherwise leave no surface trace whatsoever.