I created a Door that that looks like a bookcase for a class in College. We were told to make a door with animation, but I wanted to go a little further so I designed a door using Unity's Probuilder. 

  The first picture is a front view showcasing the bookcase.

   The second is a picture of the bookcase opened revealing that it's in fact a secret door. 

  Third picture is the bookcase being used in a library setting as just a book case and then among them is the one that does open.