History is a strange experience. The world is quite small now; but history is large and deep. Sometimes you can go much farther by sitting in your own home and reading a book of history, than by getting onto a ship or an airplane and traveling a thousand miles. When you go to Mexico City through space, you find it a sort of cross between modern Madrid and modern Chicago, with additions of its own; but if you go to Mexico City through history, back only 500 years, you will find it as distant as though it were on another planet: inhabited by cultivated barbarians, sensitive and cruel, highly organized and still in the Copper Age, a collection of startling, of unbelievable contrasts.