The Aizhai bridge, the world's highest tunnel to tunnel bridge, at 336 meter-high (1,102 feet) and spanning 1,176 meters (3,858 feet), officially opens to traffic in Jishou, central China's Hunan province on March 31, 2012. Aizhai is also the fourth suspension bridge in China to cross a valley so wide it seems to be connecting two mountain ranges, and of the world's 400 or so highest bridges, none has a main span as long as Aizhai. CHINA OUT AFP PHOTO (Photo credit should read STR/AFP/Getty Images)