Near Kilkea in County Kildare, a circular feature roughly forty metres across lies invisible to anyone walking the fields above it, yet shows itself clearly from altitude as a ghostly ring pressed into the cropmarks of a summer photograph. Cropmarks form when buried features, walls, ditches, or filled pits, affect how plants grow in dry conditions; crops above a filled ditch tend to grow taller and greener, while those above a buried wall may be stunted and pale. The result, unremarkable at ground level, can be read like a diagram from the air.

This particular enclosure was identified from Google Earth aerial imagery, specifically from photographs dated 25 June 2018, when dry summer conditions would have drawn out exactly the kind of differential growth that makes buried archaeology legible. The roughly circular outline, a form consistent with the ringforts and enclosed farmsteads that were common features of early medieval rural Ireland, measures approximately forty metres in diameter. Ringforts, known in Irish as raths or lios, were typically the enclosed homesteads of farming families, surrounded by one or more earthen banks and ditches. At forty metres, this falls within the typical size range for a single-family enclosure, though without excavation, the date and function of what lies beneath remain unknown.

Because the enclosure exists only as a cropmark, there is nothing visible to a visitor standing in the field. The site is, in practical terms, an aerial phenomenon, something that exists in photographs rather than in the landscape as most people experience it.