The enclosure at Kilsough South, County Dublin belongs firmly to that last category. It exists now only in a single aerial photograph, a ghostly oval outline pressed into the soil of a south-west-facing slope, invisible to anyone standing on the ground and long since buried beneath a housing development.

The record of this site rests on one image, catalogued as CUCAP BGL 4, which shows a cropmark of an oval enclosure roughly 60 metres in length on its north-south axis. Cropmarks of this kind, visible from the air under the right conditions of drought and low sun angle, appear when buried features such as ditches or walls affect the growth of surface vegetation above them, creating faint differences in colour or height that the naked eye on the ground cannot detect. The enclosure's original function is unknown from the available evidence, though oval enclosures of this general type in Ireland are frequently associated with early medieval settlement or with earlier prehistoric activity. The site was compiled by archaeologist Geraldine Stout and uploaded to record in August 2011.

There is, practically speaking, nothing to see here. The housing development that covers the site leaves no visible trace of what lies beneath, and no surface feature marks the location of the enclosure. For most visitors, the interest lies less in the place itself than in the idea of it, the knowledge that beneath ordinary suburban ground, a large oval boundary of some kind endures in the soil, detectable only when conditions conspire to make it briefly legible from above. The CUCAP aerial photograph archive, where the original image is held, offers the closest thing to a view of what was once there.