It has no walls, no mound, no visible trace at ground level. The only reason it is known to exist at all is a pair of aerial photographs taken in the summer of 1971, in which the crop growing over it betrayed a buried circular ditch below, its outline emerging as a faint but distinct ring against the surrounding field.

These features are known as ring-ditches, and they are among the more enigmatic entries in Irish archaeology. A ring-ditch is typically the ploughed-down or eroded remains of a circular earthwork, often interpreted as a prehistoric burial monument, though without excavation it is rarely possible to say more than that. What makes the Foulksrath example particularly interesting is that it is not alone. The immediate area around this stretch of the Nore valley contains a remarkable concentration of similar features, with well over a dozen ring-ditches recorded in the vicinity. Cropmarks like these appear when buried ditches or pits retain more moisture than the surrounding soil, causing the plants rooted above them to grow taller or stay greener longer, differences that become readable only from altitude, and often only in dry summers when the contrast is sharpest. The Foulksrath ring-ditch was captured in photographs taken on 16 July 1971 and confirmed again in images from 10 July 1973, both occasions during the kind of dry mid-summer conditions that make cropmarks legible.