If you come to D.C., do not skip a visit to the Library of Congress.
Don’t be impressed by the statistics. The largest library in the world—a campus of eight buildings, housing about 150 million items—you'll never see it all, or even a significant portion of it.
Do be impressed by the interior of the Jefferson Building. It is gorgeous. You don't need a plane ticket to Europe to see stunning architecture. It's right here in D.C. and in, of all places, a library. You can either walk around on your own or join the free guided tour, which lasts about an hour.
Visit the Main Reading Room. You can't take pictures there, so memorize every bit of detail that you can about this magnificent room. They have a number of rare, modern first editions, from authors ranging from Mark Twain to Dr. Seuss, as well as a Gutenberg Bible.
Wander through the various reading rooms and before you know it, hours will have passed and you'll have barely scratched the surface. You’ll want to come back.
You don't have to be a bookworm to appreciate this institution. The Library does have a multimedia collection; it even offers tips on how to preserve your own digital photos.
Under normal circumstances, to see the centerpiece of the world's largest library, the Jefferson Reading Room, you have to go upstairs to the observation deck merely to gawk and ogle (and take "mental" pictures since there is no photography allowed). However twice a year, the Library does open this room to the public free of charge on Columbus Day Weekend in October and President's Day Weekend in February. Not only can you take pictures, you can also see the specific spots that were featured in the National Treasure films (sorry, no Book of Secrets!)
But if you're not able to make it during those weekends, you can access the room and stacks by applying for a free library card (after all, it's a library). Head over to the first floor of the James Madison Building directly across the Jefferson Building on Independence Ave. They may ask you if you're going to do research; just say "yes," show proper photo ID and fill out their form. Then you'll be asked to get a picture taken. Wait for a few minutes, and voila, you have your card! Now go back over the Jefferson Building and get your bookworm on..