Others exist only as whispers in a field, visible not to the eye on the ground but to a camera lens carried high above it. At Farranliney in County Tipperary, three rectangular enclosures survive as cropmarks, the kind of ghostly imprint that only reveals itself from the air when differential growth in grass or grain betrays what lies beneath the soil.

Cropmarks form when buried features, such as ditches or walls, affect the moisture and nutrients available to growing plants above them. A filled-in ditch, for instance, retains more moisture and produces lusher, darker growth, while a buried wall does the opposite. At Farranliney, an aerial photograph captured three conjoined rectilinear enclosures, each defined by a fosse, which is a ditch dug as a boundary or defensive feature. The three enclosures sit together, sharing boundaries, and the central one has an entrance oriented to the east. Beyond that orientation, the photograph offers no further clues about date or function, and the site has left no obvious surface trace. Without the aerial image, this particular arrangement of ancient boundaries would remain entirely invisible.