Others exist only as faint discolourations in a field of crops, legible solely from the air and only at the right moment in the growing season. The ring-ditch at Castlehyde in north County Cork belongs firmly to the second category. Invisible at ground level, it showed itself briefly in July 1989 as a cropmark, the kind of ghostly impression left when buried ditches or pits cause the vegetation above them to grow or dry out at a slightly different rate than the surrounding soil. What appeared in that aerial photograph was the outline of a small circular enclosure, roughly fifteen metres in diameter, along with two closely spaced parallel linear cropmarks that run outward to the south-west before turning north-westwards across the field.

A ring-ditch of this scale is typically the eroded remnant of a prehistoric burial monument, most commonly a round barrow whose central mound has long since been ploughed flat, leaving only the circular fosse, or ditch, that once surrounded it. The parallel linear cropmarks extending from the enclosure are harder to categorise without excavation; they might represent a former field boundary, a trackway, or some other feature associated with the enclosure itself. The aerial survey that captured this was conducted in July 1989, a month when dry summers tend to bring buried features into sharp relief across Irish farmland. Without ground investigation, the precise date and function of the enclosure remain open questions.