The movies National Treasure and National Treasure: Book of Secrets are both filmed in Washington DC.
As the name suggests both the films are about treasure hunt.
In the first movie the character of Dr Abigail Chase played by Diane Kruger is shown as working at The United States National Archives and Records Administration (NARA) which is an independent agency of the United States government charged with preserving and documenting government and historical records and with increasing public access to those documents. Its website address is http://www.archives.gov
Two other important agencies mentioned in the movie are Department of Homeland Security and the FBI. Both are situated in Washington DC. The FBI headquarters are at J Edgar Hoover building. For its website visit http://www.fbi.gov
In the second movie National Treasure: Book of Secrets the book that has been passed on from President to President, contains vital clues to that will take the lead character Ben Gates (Nicolas Cage) to the treasure is at The Library of Congress.
This is the research library of the United States Congress and is the oldest federal cultural institution in the US. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and holds the largest number of books (with the British Library being second at about 14 million books.