The story of the Aztec empire is one wrapped in myth and legend. In less than 200 years they transformed themselves from a band of wandering nomads to the greatest civilization the New World had ever known. What records remain of this amazing feat indicate they did it through brilliant military campaigns and by ingeniously applying technology to master the harsh environment they faced. They built their capital city where no city should have been possible: in the middle of a lake. They quickly transformed marshes into rich agricultural land surrounding an urban center that rivaled any city in the world at the time. They called it Tenochtitlan. When the Spanish conquistadors arrived there in 1519, and saw its gleaming pyramids, temples and places, grand canals filled with boats, enormous causeways crossing miles of lake from the mainland with aqueducts bringing fresh running water to the massive city, they actually thought they were dreaming.