The secret Annexe was the hideout that the Franks and more were hiding in. The entrance was a secret bookshelf in an office that could open up that goes to where they lived. They lived there almost 2 years. Then once it was discovered they made the ground floor a museum and people could actually see the real pieces of her diary. Plus you can see inside the Annexe, it has become a big tourist spot.

The secret Annexe