It is a circular enclosure, the kind of ancient boundary that might once have enclosed a farmstead, a ritual space, or a defended settlement, and it is known to archaeology almost entirely because a camera, pointed downward from an aircraft, caught something the naked eye at ground level cannot see.

The enclosure was identified from an aerial photograph taken in July 1968 as part of the Cambridge University Collection of Aerial Photography. Cropmarks of this kind appear when buried features, ditches or banks that have long since flattened and silted over, still influence how grass and crops grow above them. In dry summers especially, a filled-in ditch retains more moisture than the surrounding soil, and the vegetation above it stays greener or grows taller, tracing the shape of whatever lies beneath. The circle that appeared in that 1968 image is precisely this kind of ghost, a buried boundary announcing itself through the behaviour of the grass above it. When the site was visited on the ground in 2000, there was nothing to see. Level terrain, ordinary pasture, no earthwork, no hollow, no rise. The enclosure had left no surface trace whatsoever.