Source: Rise Studio
During the construction of the monument on Mount Rushmore, architect Gutzon Borglum wanted to create a secret room where future generations would find the fundamental records of and information about the USA's history. For this purpose, he excavated a cave behind the head of Abraham Lincoln. Soon after, however, Borglum died, and his plan was not completed. In 1998, more than 50 years after his death, copies of important documents and the memoirs of various presidents were placed inside the unfinished hall, which now serves as a time capsule.