The catch is that nobody has ever seen it from the ground. The only evidence for its existence is a cropmark, the kind of faint shadow that buried features cast on growing crops when viewed from the air, visible in aerial photographs taken in the mid-1990s.

Cropmarks form because buried ditches or banks alter the moisture and nutrients available to roots above them, causing crops to grow slightly taller or shorter in patterns that trace the outline of whatever lies below. In this case, the photographs revealed what appears to be the southern arc of a large, possibly oval enclosure on a gradual north-facing slope just off the flat crest of a ridge. Only the southern side is clearly defined. To the north, the ground drops away naturally before levelling briefly and then falling steeply toward a field boundary, and it is thought that this northern field boundary may mark the approximate edge of the enclosure, if enclosure it truly is. Nothing breaks the surface of the tillage field to suggest anything unusual lies underneath.

The conditional nature of the identification is worth sitting with. This is a monument that exists, for now, in the uncertain space between possibility and proof, known only through the geometry of crops on a summer morning captured from altitude. Whether excavation or further survey will ever settle the question is unknown.