Ruins of Templo Mayor of Tenochtitlan in Mexico City. Clockwise from top left: ear flare, Tlaloc mask (2), lightning bolt scepter(Mirsa Islas Orozco/Courtesy of ...

The Tibetan Plateau is one of Earth's harshest environments, encompassing nearly a million square miles of land thrust two and a half miles skyward, blanketed in cold, thin air that's difficult to ...