Fitted stones in wall at Sacsahuaman, Peru. It is not known how the pre-Incas could have transported such enormous stones nor could have cut them to fit so exactly, not only on the surface, but also in depth, and finally, why they were set at such odd angles – perhaps for economy of cutting or to prevail against earthquakes. (Photo: J. Manson Valentine)

From Mysteries of Forgotten Worlds by Charles Berlitz