The enclosure at Raheenapisha in County Kilkenny is one such place. Nothing rises above the surface of the field to mark it out, yet from the air its outline is unmistakeable: a roughly circular form, around forty metres across, ringed by a wide outer fosse. A fosse is simply a ditch, in this case broad enough to be clearly visible even as a cropmark, the buried feature drawing moisture differently from the surrounding soil and leaving its ghost in the grain.

The site was identified on an aerial photograph taken on 15 July 1968, part of the Cambridge University Collection of Aerial Photography. Cropmarks of this kind tend to appear in dry summers, when shallow soils above buried ditches retain just enough moisture to keep the vegetation above them greener or more vigorous than the rest of the field. The 1968 photograph also captured a north-to-south field boundary running immediately to the east of the enclosure, a boundary that has since been levelled and no longer exists on the ground. The enclosure itself, likely the remains of a ringfort or similarly enclosed settlement, would have been a commonplace feature of the early medieval Irish landscape, though its precise date and character remain unknown.