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 us that 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. But after Columbus set foot in the Americas, an endless wave of explorers, conquistadors, and settlers arrived, and with each of their ships came a Noah's Ark of plants, animals—and disease. In the first 100 years of contact, entire civilizations were wiped out and the landscape was changed forever. 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.