Built in the 1970s as a bomb shelter, the underground city of Dixia Cheng in Beijing, China, is often referred to as the Underground Great Wall on account of its numerous tunnels. When it was constructed it apparently boasted schools, hospitals, and sleeping halls. But it has never needed to be used and in 2000, it was opened to the public for tours. Guided visits didn’t last long, however. Since 2008 a notice by the entrance at Xidamochang Jie has read that the complex is closed for renovations following a safety inspection.
Photo credit: Samuel Tan / Wikimedia Commons