Somewhere beneath the flat tillage fields of Courttown in Co. Kildare, a circular ditch lies completely invisible at ground level, its presence betrayed only from the air. What survives is not a monument in any conventional sense but a cropmark, the faint signature of a buried ring-ditch recorded on aerial film in 1991 by Dr. Gillian Barrett. A ring-ditch is generally understood to be the filled remnant of a circular earthwork, often associated with prehistoric funerary or ceremonial activity, where the original banks and mounds have long since been ploughed flat, leaving the ditch fill to affect crop growth in ways that become legible from altitude. The soil inside a former ditch retains more moisture, and the crops above it grow taller or ripen differently, producing a pattern that can be photographed under the right conditions.

This particular feature is one of a remarkably dense cluster of such cropmarks concentrated in a roughly rectangular area of approximately 650 metres east to west and 350 metres north to south in the same level farmland. The monuments were identified from multiple aerial photographic sources, including the Cambridge University Collection of Aerial Photographs, the Geological Survey of Ireland, and Dr. Barrett's own survey work. Across the broader cluster, more than a dozen individual features have been catalogued, with a couple of outliers lying some 250 metres to the south and another roughly 220 metres to the north-west. The ring-ditch at Courttown, captured on aerial photograph GB91.EA.21 during Barrett's 1991 survey, sits within this concentration, suggesting the area was once a meaningful landscape, likely used over a long period, though the precise date and nature of the original structure cannot be determined from the cropmark alone.