The National Archives is located north of the National Mall in Washington D.C. The huge building was opened in 1935. It stores and exhibits the original copies of three fundamental historical documents of the US: the Declaration of Independence, the Constitution, and the Bill of Rights. During the night, the documents are lowered into an underground vault, where they are protected by the most up-to-date security equipment; the vault is supposed to survive even a nuclear blast. The Archives is also responsible for preserving government and historical documents. Most of the documents stored in the National Archives are in the public domain, excluded from copyright protection.