The Library of Congress is incomparable. The writer has been a docent there for more than 5 years and still looks forward to his every visit. It is the largest library in the world. It's collection includes materials in every language in the world, in books, manuscripts, periodicals, maps, prints, photographs, movies, videos, music, etc. Its main building, the Jefferson Building is a stunning example of Italian Renaissance design with a with Beaux Art interior decoration that will excite and bewilder. The collection and displays consist of rare books and other treasures. The best part is that it is accessible to all, not just "qualified" scholars. You don't have to pay to access the materials or to tour the Library. Docent led tours of the public spaces are free. It would be a mistake to visit Washington and miss this unique institution of the US government.