Beneath a field in Moortown, Co. Kildare, a circular enclosure lies entirely invisible to anyone standing on the ground above it. Its existence is known only because of what crops do when their roots meet buried archaeology: they grow differently, and from the air, on the right day, those differences resolve into shapes.

What appeared in a Google Earth aerial photograph taken on 28 June 2018 is a cropmark of a bivallate circular enclosure, meaning the outline of a circular space once defined by two concentric banks or ditches. Cropmarks of this kind form when soil disturbance from ancient features, whether silted-up ditches or the compacted remains of banks, affects how vegetation above them responds to moisture and nutrients, particularly during dry spells in summer when contrasts become most legible from above. The circular enclosure form is one of the most widespread in the Irish landscape, associated broadly with early medieval settlement, though dating any specific example without excavation is rarely straightforward. The bivallate form, with its doubled circuit, may suggest a site of some elaboration or status, though again the ground has not been tested. Notably, the same feature did not appear on a separate Digital Globe aerial photograph of the area, a reminder of how contingent this kind of evidence is, dependent on the precise timing of a flyover, the state of the crops, and the weather in the weeks before.