27. Moscow Metro-2, Russia

Between the secret tunnels and ghost trains, you would think it was the plot of a fantasy movie unless you heard about the Moscow Metro-2. According to intelligence, the KGB built this underground metro system 600-feet underground in case of a nuclear disaster. 

The lines connect important government buildings, the airport, and secret service headquarters. No one really knows what it looks like, but it was built at the beginning of Stalin's reign. We guess you wouldn't want to be here because that would mean that a nuclear disaster has struck.