Others exist only as shadows in a field, legible solely from the air and only under the right conditions. At Castlehyde in County Cork, two conjoined circular enclosures, each roughly thirty metres in diameter, fall into that second category. They survive not as upstanding remains but as cropmarks, the faint differential growth patterns in vegetation or soil that betray buried features beneath the surface. When crops grow over buried banks or ditches, they absorb moisture and nutrients unevenly, and from altitude that uneven growth reads as a ghostly outline of whatever once stood or was dug there.

The pair of enclosures came to light in an aerial photograph taken in July 1989 as part of the Cork Aerial Survey and Aerial Photography programme. What was captured was the impression of two circular earthen banks sitting side by side, their outlines pressed together in that double-circle form sometimes described as a figure-of-eight plan. Circular enclosures of this general type are a common feature of the Irish landscape, associated broadly with the early medieval period, though their functions varied considerably, from domestic farmsteads to enclosures with ritual or funerary purposes. The pairing of two such enclosures is less common and raises questions about sequence, purpose, and the relationship between them that the aerial image alone cannot answer.