High in the skies over Kazakhstan, space-age technology has revealed an ancient mystery on the ground. Satellite pictures of a remote and treeless northern steppe reveal colossal earthworks — geometric figures of squares, crosses, lines and rings the size of several football fields, recognizable only from the air and the oldest estimated at 8,000 years old. The largest, near a Neolithic settlement, is a giant square of 101 raised mounds, its opposite corners connected by a diagonal cross, covering more terrain than the Great Pyramid of Cheops. Another is a kind of three-limbed swastika, its arms ending in zigzags bent...