A ring-ditch, roughly twelve metres across, announces itself only as a cropmark, the kind of faint discolouration that appears in aerial or satellite imagery when buried features alter how plants grow above them. Where a fosse, or enclosing ditch, was once cut into the ground, the soil retains moisture differently, and in dry conditions the grass or grain above it grows at a slightly different rate, tracing the original shape in shades of green or gold. The circle at Grevine is small, about the width of a modest house, and defined by just such a fosse.

Ring-ditches of this kind are found across Ireland and are generally understood to be the remnants of prehistoric funerary or ceremonial monuments, the ditches that once surrounded a burial mound or a low earthen barrow, long since ploughed flat. The mound itself may be entirely gone, leaving only the encircling cut in the subsoil to hint at what once stood here. This particular example was identified and reported by Jean-Charles Caillère, who spotted it in satellite imagery on Apple Maps, a reminder that some of the quieter archaeological discoveries of recent years have come not from excavation but from patient scrutiny of publicly available imagery.