The US military built a secret city under the ice sheet of Iceland, during the Cold War; in the Scotland of the 1800s Burke and Hare lurked in the Edinburgh Vaults; in Turkey the subterranean tunnels of Cappadocia housed up to 20,000 people; the salt mine town of Wieliczka in Poland was built in the 13th century; and the ancient city of Petra, Jordan, was lost for centuries from the late 8th century. Packed with intriguing and haunting photographs this new book charts the many hidden sites of our world, from China, Russia and Poland to the mysterious underground dwellings in the cities of Canada and the USA.