Qiao Guohua patrols a 5-mile stretch of the Great Wall of China. Roughly a third of the wall's 12,000 miles have crumbled to dust, and saving what's left may be the world's greatest challenge in cultural preservation.
Two of the names carved into the Great Wall, in this case near Badaling, China. Authorities hope to cut down on graffiti by giving tourists a designated spot to leave their marks.
David Guttenfelder /AP