9. Fort Knox, Kentucky, USA
Media Source: mentalfloss.com
The United States Army post known as Fort Knox is also the United States Bullion Depository and has 5000 tons of gold bullion stored inside. The way this building is protected is a pure masterpiece. There are four surrounding fences, video cameras, armed sentinels, granite walls and vault doors. Even the last vault has a secret code that is split between staff members and each one of them only knows a part of the code. Also, there are 30,000 soldiers from the military camp awaiting for a call. The next thing is something from a sci-fi movie!