It exists, for practical purposes, only from the air, and only under the right conditions: a dry spell, a particular angle of light, and a growing crop sensitive enough to betray what lies beneath the soil.

The enclosure at Rehill was identified through a circular cropmark captured in an aerial photograph taken on the third of August 1996. Cropmarks of this kind form when buried features, walls, ditches, or filled pits, affect the moisture available to plants growing above them. Soil that once filled an ancient ditch tends to retain more water, producing a line of lusher, darker growth; compacted foundations do the opposite. Seen from above at the right moment, these differences in crop colour or height can outline structures that vanished from the surface centuries or millennia ago. The circular shape at Rehill suggests an enclosure, possibly a ringfort or similar enclosed settlement, of the kind once common across the Irish countryside. At ground level, there is nothing whatsoever to indicate its presence.