And we thought those elaborate hidden facilities in the Bond movies were fun but implausible.
Guess the key is having the approval of the government.
Remember, we had the secret underground quarters for Congress at Greenbrier.
If you really want to let your imagination run wild, search for "underground US bases" and you'll find a number of pages like this, which believe there are over a hundred underground bases in the US. Some believe they are inhabited by aliens or underground people [insert spooky music here].