Somewhere beneath a tilled field in Barberstown, County Kildare, a circular enclosure roughly forty metres across lies entirely invisible at ground level, betrayed only from the air. What makes this site quietly unusual is that it has never been excavated, never been mapped on the ground, and exists in the record almost entirely as a pattern of colour in aerial photography. The enclosure shows up as cropmarks, the differential growth in cereal crops that occurs when roots penetrate the looser soil of ancient filled-in ditches more easily than the compacted ground around them. On a warm dry summer, what was once a substantial earthwork can re-emerge, ghostlike, in the geometry of a growing field.

The site was first identified on an Ordnance Survey Ireland orthophoto taken in 1995, and has since been confirmed on later satellite imagery through Google Earth and Bing. The cropmarks reveal two concentric fosses, that is, ditches forming a double ring around a central circular area, a configuration associated with enclosed settlements or ceremonial sites from the prehistoric through to the early medieval period in Ireland. A second, considerably fainter cropmark lies approximately fifty metres to the south-east and may represent the remains of a ringbarrow, a type of low circular burial mound typically dating to the Bronze Age. The possible pairing of an enclosure and a nearby ringbarrow would not be unusual in the Irish midlands, where such features often cluster in landscapes that were already ancient when the first written records began.