National Geographic : 2011 Apr
DEPARTMENTS ngm.com FOR SUBSCRIPTIONS, GIFT MEMBERSHIPS, OR CHANGES OF ADDRESS, CONTACT CUSTOMER SERVICE AT NGMSERVICE.COM, OR CALL 1 800 NGS LINE 647 5463 . OUTSIDE THE U.S. AND CANADA PLEASE CALL +1 813 979 6845. On the Cover With 3-D data, experts helped shape this image of Machu Picchu, "lost city" of the Inca. The conical roof sits on the Temple of the Sun. Art by Dylan Cole Sources: Instituto Nacional de Cultura, Peru; Center for Advanced Spatial Technologies, University of Arkansas; Cotsen Institute of Archaeology, UCLA; Vincent R. Lee DIANE COOK AND LEN JENSHEL O Online Adventures Take a virtual walk on New York's High Line (above). Read Hiram Bingham's account of his Machu Picchu discovery. Learn more about a photogra- pher's volcanic encounter. Editor's Note 4 National Geographic on TV 6 Letters 10 Your Shot 12 Visions of Earth 14 Inside Geographic 146 Flashback THE BIG IDEA Perennial Grains 30 Annual grains feed the world, but they create perennial problems. POPULATION Marriage Across Color Lines Once illegal in many states, interracial marriages are on the rise in the U.S. GEOGRAPHY State Rock Stars California was among the first to name---and the first to nearly disown---its state rock. HISTORY Polar Dogs and Ponies An aeronautical chart of a New Zealand-to- Antarctica route honors four-legged explorers. CULTURE Zeroing in on Corruption Indian officials who stick out a hand for extra cash are chastened with a zero-rupee note. FOSSILS Prehistoric Big Birds An ancient flier's 17-foot wingspan offers clues to how supersize birds flew.