The Most Secret Places in the World - And the wild theories about what really happens inside. In the modern world, places are supposed to be accessible. People move freely around the country they live in and even between countries. 

However, the most interesting, fascinating and mysterious locations in the world, even today, are strictly off limits to just about everyone. 

Most of the places on this list are only accessible to those with the proper clearances, but some are not accessible to anyone at all. Regardless of the status of the places on this list, if you're searching for them, you absolutely do not have the proper access to visit them. 

The tantalizing status of the unknown and the secret makes these spots remarkable. You probably have your own theories about what goes on at some of these locations. If you don't, we'll provide some. You may not have ever heard of a few of these places. In fact, there are government facilities in the United States -- and around the world -- that are unknown to people even in the highest levels of government. 

Let's find out why.