Capitol complex
U.S. Botanic Garden
The national conservatory is one of the least visited attractions around the Mall, and that is one of the best reasons to visit. The botanical collection is extensive, the climate is often a welcome respite, and the catwalk through the leaf canopy in the jungle room is a favorite. Bartholdi Park, south of the conservatory, is small but majestic, centered around the Bartholdi Fountain.
Library of Congress
Originally founded by the third U.S. president, Thomas Jefferson, this grand building, also called the Jefferson Library, has the largest collection of books in the world. The most popular points of interest are the massive main reading room and Great Hall. On the Winter and Summer solstices the Great Hall is filled with an odd silver glow that gives the impression you are surrounded by floating clouds, and this makes those days the most crowded. The main reading room is known as the Sacred Room, and is absolutely stunning. You must be 18 or older to use the reading rooms and have a user card, which can be obtained by presenting a driver's license or completing a self registration form. Guided tours will not bring you into the reading room, but will take you up in the dome, where you can see the room in its full glory. There are also a number of rotating exhibitions from the Library's vast collection on display at any one time, as is a Gutenberg Bible.
Capitol Building
The center of the legislative branch of America is home to the House of Representatives and the Senate, as well as numerous impressive paintings, statues, historical exhibits, and one magnificent dome. A new Visitor Center recently opened, which features a exhibition of the history of the Capitol and of Congress. Tours of the Capitol building can be arranged through the Visitor Center website or by calling or emailing your Representative's or Senator's office a few weeks in advance. Tours start from within the Visitor Center. You may not bring food/drinks inside. Only the smallest and thinnest bags will be allowed. If lines for security are long, an alternative is to use the tunnel from the Library of Congress.
Supreme Court
This is the center of the U.S. Judicial Branch and of the three branches is the one that commands the greatest respect in American political life. Visitors can watch the court in session M-W, from October-April, with admission on a first-come, first-served basis. The rest of the year, public lectures are held every hour in the courtroom. The spiral staircases on the sides of the court room are beautiful and impressive parts of the building not to be missed. Here's a bit of trivia: the court didn't even have its own building until 1935, until then it was held in the Capitol building.
Other attractions
National Postal Museum
The Smithsonian's own philatelist Shangri-La has one of the world's largest collections of rare stamps, as well as exhibitions of how mail has been delivered throughout history, and other ways that the mail shapes culture.
Congressional Cemetery
All sorts of notables from American history found their final resting place here, from composer John Sousa to FBI founder J. Edgar Hoover.
Union Station
Not just a train station or metro stop, the grandiose 1908 Beaux Arts building by legendary American architect Daniel Burnham makes it worth a lookâthe ceremonial entrance is stunning. Open long after the museums close, it contains shops, restaurants and a cinema. A large monument to Christopher Columbus stands outside the building.
The main attractions on Capitol Hill are all concentrated in the U.S. Capitol Complex, grounds managed by the Architect of the Capitol, covering roughly the three blocks east of the Mall. These include the Capitol Building and its grounds, as well as the U.S. Supreme Court, Library of Congress, and congressional office buildings.