In a field near Boherkill in County Kildare, there is nothing obviously ancient to see at ground level. The site reveals itself only from the air, and only under the right conditions, as a ghostly circular outline pressed into growing crops. This kind of mark, known as a cropmark, appears when buried features such as ditches cause the vegetation above them to grow differently, often greener and taller over filled-in ditches where moisture collects, or stunted and yellowed where buried walls restrict root growth. The result, visible for a narrow window during dry summers, is something like a photographic negative of a vanished structure.

What the aerial evidence shows here is a circular enclosure defined by a fosse, which is simply a ditch, typically cut to delineate and defend a settlement or ceremonial space. Circular enclosures of this kind are among the most common archaeological features in the Irish landscape, ranging from early medieval ringforts used as farmsteads to prehistoric ceremonial sites, though without excavation it is rarely possible to say which category a cropmark site belongs to. An aerial photograph taken in 1990, catalogued as GB90.BB.08, first recorded this particular feature. Later imagery from Google Earth, captured in June 2018, added further detail, suggesting not just the circular enclosure itself but traces of a wider field system in the surrounding area, hinting that this was once an organised agricultural or settled landscape rather than an isolated monument.