Today in Russia, at least 1.5 million people live in cities that no one from the outside world is allowed to visit. Many don't appear on maps. Some have no road signs to indicate where they are. Still more are so cloaked in secrecy that people outside Russia don't even know what they're called.
They are Russia's 'closed cities,' a hangover from the Soviet Union when the then government went to extreme lengths to conceal locations of strategic importance. The clandestine communities housed military bases, weapons factories and secretive research facilities that those in power wanted to keep hidden from foreign eyes.