The National Archives building in Washington, D.C. houses some of the United States’ most foundational texts, including the Constitution, the Bill of Rights, and the Declaration of Independence. These three documents are collectively known as the Charters of Freedom, and could be the most closely guarded pieces of paper on the planet.

During the day these important texts are available for public viewing under bulletproof glass and constant guard. But every night (and at the press of a button, should the need arise) a special elevator pulls them underground into a custom-built armored vault.

The original vault was built in 1953 by the Mosler Safe Company. The firm was the logical choice, having previously taken on notable achievements like the gold bullion vault at Fort Knox, and a bank vault in Hiroshima that survived an atomic bomb.

The original, 55-ton Mosler Vault was the size of a walk-in closet and employed a 20-foot scissor jack to raise and lower the Charters of Freedom. A 1953 documentary shows the lift in operation here. The Mosler Vault was replaced in the early 2000s as the National Archive underwent a major $110 million renovation. The current vault, designed by Diebold, is still shrouded in secrecy.