If you look closely and do a bit of research, you will find out that the things you've been seeing your entire life have some secrets. After reading this, you won't believe that you didn't know this sooner.
The Secret Chamber Behind Lincoln's Head on Mount Rushmore
There is a cave behind Lincoln's head that was supposed to be a secret chamber. Borglum, the architect, created the room and planned to use it to store essential documents related to the history of the US. But he died before finishing it. However, Borglum's plan was completed in 1998, various historical records were stored inside, and the room became a time capsule.