In the film, the Book of Secrets is found in a balcony area of the Library of Congress . While the scene was filmed in the real building, the specific bookshelves were a temporary prop built in a vacant balcony and later dismantled. Filming and Locations

The film's climax at Mount Rushmore was the first time the landmark had been used as a major filming location since 1959's North by Northwest . The fabled treasure was "found" at Sylvan Lake in Custer State Park, about five miles away.

National Treasure: Book of Secrets expands the franchise's scope with globe-trotting action and deeper historical mysteries, such as the true story behind the Lincoln assassination. Key features of the production include massive physical sets, a heavy reliance on real historical locations, and several "easter eggs" hidden within props and dialogue. Production and Set Design

The literal "Book of Secrets" used in the film was a highly detailed prop that included a leather case with hand-cut lining and weathered pages. It contained specific historical "Easter eggs" for eagle-eyed viewers, such as Marilyn Monroe ’s autopsy report, blueprints for a flying saucer, and a letter from Woodrow Wilson.