This former diamond mine in Russia is an unsettling sight, especially if you're a helicopter pilot. The site was established during the time of the Soviet Union and was continually dug until the job became far too difficult (not to mention dangerous) and was abandoned. There's an added risk for travellers wanting to see the impressively-sized hole, too, being that the pit in question is so large that helicopters are forbidden from flying over as bizarre vortexes can be created by the structure.
3. Underwater City - China
The city of Shi Cheng in China was founded over 1,300 years ago, but for more than 50 of them it's been sitting underwater. The Xin'an Hydro Plant was responsible for the flooding in the 1959 creation of the manmade Qiandao Lake, meaning the city's inhabitants were forced to relocate. The city has become something of a diver's paradise due to its ancient architecture and beautiful, mysterious appeal afforded it by being completely submerged and almost completely inaccessible.
