In a field near Prumpelstown in County Kildare, there is nothing visible to the naked eye at ground level. No mound, no stone, no obvious interruption in the soil. The only evidence that something ancient lies beneath comes from the air, where a circular cropmark traces the outline of a fosse, a broad enclosing ditch, roughly twenty metres across at its widest point.

Cropmarks appear when buried features affect how plants grow above them. A filled-in ditch retains more moisture than the surrounding subsoil, so the crops or grasses directly above it tend to grow taller or stay greener for longer, producing a faint but legible pattern when viewed from height. In this case, aerial photographs catalogued under reference CUCAP BOC 81 and 84 reveal a near-perfect circle, consistent in form with either a ring-barrow or a ring-ditch. The two are closely related. A ring-barrow is a burial monument of prehistoric origin, typically consisting of a central mound surrounded by a circular ditch and sometimes an outer bank. A ring-ditch is the term used when the central mound has been ploughed or eroded away entirely, leaving only the enclosing fosse. Whether Prumpelstown preserves a burial at its centre, or whether any such deposit has long since vanished, is not known from surface evidence alone. Sites of this type are found widely across Ireland and Britain, and most date to the Bronze Age, though some belong to the Iron Age or even earlier Neolithic traditions.