Mount Rushmore is widely recognized as one of America's most famous landmarks, appearing in countless films and TV shows.
As it turns out, the giant sculpture in South Dakota holds a secret: A room, hidden behind the chiseled granite face of Abraham Lincoln contains a vault full of documents that, it is hoped, will someday be discovered by a future civilization to learn more about the United States, according to the Daily Mail.
Tourists visiting Mount Rushmore are not able to see the Hall of Records because its location makes it very difficult to access.
The monument was originally planned to be much larger, featuring images of major moments in U.S. history alongside George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln. However, sculptor Gutzon Borglum's plan had to be reduced to just the four presidents when it became apparent that the larger work was an unrealistic goal.
Borglum did, however, include a hidden room behind the monument known as the Hall of Records. The secret vault, which appears as a stone doorway in a small valley behind the president's carved face, was intended to hold important documents that future generations could find in order to learn more about the country's history.
"You may as well drop a letter into the world’s postal service without an address or signature, as to send that carved mountain into history without identification," said Borglum in 1939, explaining his plan to include identifying documents with the Mount Rushmore sculpture, according to the National Park Service.
Construction on the Hall began in July 1938, when a 70-foot tunnel was dug into the side of the mountain. Borglum died before the full project could be completed, which halted construction of the Hall of Records for decades until it was revived in the 1990s.
With the new construction, the Hall was completed, and porcelain enamel panels displaying important American documents such as the Declaration of Independence, the Bill of Rights, and the Constitution were placed inside of a titanium vault in the stone Hall.
The titanium vault holding the enamel panels is covered by a granite capstone, which is inscribed with a quote from Borglum. "… breathe a prayer," reads the etching, "that these records will endure until the wind and rain alone shall wear them away."