In a tilled field near Sheean in County Kildare, something circular and long-buried has left its mark on the land, visible not to the eye on the ground but to a camera looking straight down from above. A cropmark, roughly fifteen metres in diameter, traces what appears to be a small enclosed area once ringed by a fosse, a defensive or boundary ditch, that has since been filled in and smoothed over by centuries of agriculture.

Cropmarks form when buried features affect how plants grow above them. Filled ditches tend to retain more moisture than the surrounding subsoil, producing lusher, darker growth in dry conditions, while buried walls or compacted surfaces can have the opposite effect, leaving paler, thinner strips. In this case, the circular outline of a back-filled fosse, a ditch that would originally have encircled some kind of enclosure, showed up in aerial imagery in the kind of detail that ground-level inspection would entirely miss. Enclosures of this type are scattered across the Irish midlands and come in a considerable range of sizes and dates; a diameter of around fifteen metres places this one at the smaller end of the scale, more consistent with a ringfort or an early medieval farmstead boundary than with a large ceremonial or defensive site, though without excavation any such interpretation remains provisional.