GREAT WALL TOUR U.S. Defense Secretary Robert M. Gates receives a tour at the Great Wall of China in Mutianyu, China, Jan. 12, 2011. Gates wrapped up a four-day trip to China by visiting the People's Liberation Army 2nd Artillery Corps and the Great Wall. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 582422-T-OMM76-562.jpg Photo Gallery