Others exist only as a shadow in a field, visible solely from the air, on the right day, in the right season. The ring-ditch at Woolengrange in County Kilkenny belongs entirely to the second category. It is known from a single aerial photograph taken on 13 July 1989, in which the circular outline of a buried feature, roughly 20 metres across, showed up as a cropmark against the surrounding farmland.

Cropmarks form when buried archaeology affects how plants grow above it. A buried ditch, for instance, retains more moisture than the compacted soil around it, causing the crops directly overhead to grow taller and greener, or to ripen at a slightly different rate. From ground level, the difference is imperceptible. From the air, particularly during a dry summer when stress on vegetation is greatest, the pattern can emerge with startling clarity. The Woolengrange ring-ditch was caught in exactly this way. A ring-ditch of this kind is generally understood to be the remnant of a circular funerary monument, most likely prehistoric, where the original mound has long since been ploughed flat, leaving only the encircling ditch as a trace beneath the surface. At approximately 20 metres in diameter, it sits within a range typical of Bronze Age burial monuments found across Ireland. A field boundary running north to south lies immediately to the west, suggesting the landscape has been actively farmed around and over the site for a considerable time.