Vast, unidentified, structures have been spotted by satellites in the barren Gobi desert, raising questions about what China might be building in a region it uses for its military, space and nuclear programmes. 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...