Stand in a tillage field near Courttown in County Kildare and there is nothing to see. No mound, no earthwork, no trace of anything below the surface that might suggest the ground has a history. Yet a single aerial photograph taken in 1973 tells a different story: the faint outline of a fosse, a defensive or boundary ditch, curving around a roughly circular area no more than twenty metres across, visible only because the crops above it grew differently from those on either side. That kind of ghostly impression, recorded in the tonal differences of growing grain, is known as a cropmark, and it is often the only evidence left of monuments that have been ploughed flat over centuries of farming.

This particular enclosure is one feature within a remarkably dense cluster of such cropmarks spread across a roughly rectangular block of land measuring approximately 650 metres east to west and 350 metres north to south. Several further sites appear as outliers beyond that core area, one group lying roughly 250 metres to the south and another around 220 metres to the north-west. The cluster was identified from multiple aerial photographic sources, including surveys carried out by Cambridge University and by Dr Gillian Barrett, whose aerial work has contributed significantly to the mapping of levelled monuments across Ireland. The enclosure itself, given its modest diameter and the circular fosse surrounding it, has been interpreted as possibly a ringditch or a ringbarrow, both of which are typically associated with burial or ritual activity in prehistoric and early medieval Ireland. A ringbarrow consists of a low mound enclosed by a ditch and outer bank, while a ringditch is the ditch alone, the central mound having disappeared entirely. In this case, nothing at all survives above ground.