100 Places You Will Never Visit: The World's Most Secret Locations

The world is full of secret places that we either don't know about or couldn't visit even if we did know about them. Some lie under our feet, like London's Whitehall tunnels, Moscow's hidden subway, and the Gaza Strip smuggling passages. Others—like the USA's Mount Weather Emergency Operations Center and Mount Baekdu, a mountain lair purportedly built by Kim Jong-Il in North Korea—are so confidential that their existence is not even acknowledged by governments.