In two images, available on Google Earth, reflective rectangles up to a mile long can be seen, a tangle of bright white intersecting lines that are clearly visible from space.

Other pictures show enormous concentric circles radiating on the ground, with three jets parked at their centre.

In one picture from 2007, a mass of orange blocks have been carefully arranged in a circle. In a more recent image, however, the blocks, each one the size of a shipping container, appear to have been scattered as far as three miles from the original site.

Another image shows an array of metallic squares littered with what appears to be the debris of exploded vehicles while another shows an intricate grid that is some 18 miles long.