In a field near Longtown in County Kildare, something circular lies just beneath the surface, invisible to anyone walking past but legible from the sky. A ring-ditch of roughly ten metres in diameter shows up as a cropmark on aerial imagery, its outline betrayed not by stone or earthwork but by the differential growth of the crops above it. Where a ditch was once cut into the subsoil and later filled in, the soil retains more moisture, and the plants rooted there grow fractionally taller or greener, drawing a ghost of the original feature across the field.

Cropmarks of this kind are one of the quieter revelations of aerial archaeology. Ring-ditches are generally understood to be the surviving traces of prehistoric funerary or ceremonial monuments, most often the encircling ditch that once surrounded a burial mound whose earthen body has long since been levelled by centuries of ploughing. The Kildare example, approximately ten metres across, sits within the modest size range typical of such features. The cropmark was identified on Google Earth aerial photography dated 28 June 2018, with the record compiled by Caimin O'Brien from details provided by Jean-Charles Caillère.