In the fields outside Nicholastown in County Kildare, something buried beneath the soil has been quietly giving itself away. Under the right conditions, a dry summer will stress the crops growing above a filled-in ditch, leaving them thin and yellowed compared to the surrounding growth. The result, visible only from the air, is a ghost outline of a structure that has not existed above ground for centuries, possibly millennia.

An aerial photograph taken in 1989 captured exactly this phenomenon at Nicholastown, revealing the cropmark of a D-shaped enclosure with an entrance facing south-east. The enclosure was defined by a fosse, which is a defensive or boundary ditch dug into the ground, its fill now producing the discolouration visible from above. A rectangular annexe is also discernible to the north of the main enclosure. Enclosures of this kind are found widely across Ireland and are associated with a range of periods and functions, from early medieval farmsteads to prehistoric settlements, and without excavation it is difficult to assign this one to a particular era. The D-shaped form, however, is a reasonably distinctive profile, and the presence of an annexe suggests a site of some complexity, perhaps used for livestock, storage, or some secondary domestic purpose alongside the main enclosed space.