The "nation's file cabinet" houses the original Declaration of Independence , the Constitution and the Bill of Rights in its magnificent rotunda.  It also houses rotating exhibits and part of the National Archives and Records Administration's more than 3 billion records.  Open: Daily 10 a.m.-5:30 p.m. except Christmas; extended summer hours. Group tours by appointment, call (202) 501-5205. Admission: Free   Metro: Archives-Navy Memorial. Related Links: National Archives and Records Administration