Before Columbus

National Geographic embarks on an expedition into the mysterious world of ancient American history to shed a different light on the history of the Americas. History books traditionally depict the pre-Columbus Americas as a pristine wilderness where small native villages lived in harmony with nature. But scientific evidence tells a very different story: When Columbus stepped ashore in 1492, millions of people were already living there. America wasn't exactly a "New World," but a very old one whose inhabitants had built a vast infrastructure of cities, orchards, canals and causeways.