Massive Underground City Found in Cappadocia Region of Turkey When the invaders came, Cappadocians knew where to hide: underground, in one of the 250 subterranean safe havens they had carved from pliable volcanic ash rock called tuff. [more inside]
Chairman Mao's Underground City is a pictorial travelogue of a small part of the tunnels that Chairman Mao had built under Beijing to serve as a nuclear fallout shelter. The intrepid urban explorers come across some surprising things. The complex, which was built by hand, could house three hundred thousand people for up to four months and had amenities such as restaurants, cinemas and roller rinks. Here's a short Travel Channel feature on the Underground City.