17 Name: National Gallery of Art East Building Location: 4th Street and Constitution Avenue NW Building Stones: Tennessee light-pink marble; street, driveway, and border of several granites Remarks: This new wing, designed by I.M. Pei, opened in 1978 to house changing exhibits and the museum's collection of 20th century art. The main part of the building is an isosceles triangle, containing two sides of equal length.

18 Name: Union Station Location: Massachusetts Avenue and First Street NE Building Stones: Vermont granite Remarks: Union Station was built to consolidate Washington's passenger train traffic into one location; it was opened to service in 1907. The station, modelled after the Baths of Caracalla in Rome, is 720 feet long; the waiting room is 120 feet wide and 219 feet long, and the vaulted ceiling reaches 96 feet above the floor. A major renovation was completed in 1989, and the building now serves as a National Visitor Center, in addition to being a terminal for train and subway service.

19 Name: The U.S. Capitol Location: Capitol Hill, between Constitution Avenue and Independence Avenue Building Stones: Center building, Virginia Aquia Creek sandstone; Senate and House wings, Lee, Mass., dolomitic marble; Rotunda floor, Seneca, Md., sandstone; columns of wings, Cockeysville, Md., white marble; center steps, Renville, Minn., granite; west elevation steps, Mount Airy, N.C., granite; west elevation balustrade, Vermont marble; interior balustrades and columns of stairs leading to House and Senate galleries and wall of Marble Room, Tennessee marble; east front exterior, Georgia White Cherokee marble (covering original Aquia Creek sandstone); 24 exterior columns, Georgia marble; interior columns, Statuary Hall, Old Senate Chamber and foyer, Maryland Potomac marble; columns in Crypt and those with corn and tobacco leaves, Virginia Aquia Creek sandstone; columns, ground floor east front addition, Colorado brecciated marble Remarks: President Washington laid the southeast cornerstone of the main building September 18, 1793, on the site chosen by L'Enfant. The north wing was completed in 1800; the south wing in 1807. Both wings were burned by the British during the War of 1812 but were restored by 1829. The dome and wings are examples of the Greek Revival style. New wings, built in the 1850's, doubled the length of the building.

20 Name: Supreme Court Building Location: East Capitol and First Streets NE Building Stones: White marble Remarks: This building, the first permanent home of the U.S. Supreme Court, was completed in 1935. Its central portion is in the style of a Greek temple with Corinthian columns and enormous sculptured bronze doors.

21 Name: Library of Congress Location: East Capitol and First Streets, SE Building Stones: Concord, N.H., granite Remarks: The main building, named in honor of Thomas Jefferson, is of Italian Renaissance design and was completed in 1897. The library has more than 86 million items in its collections, including one of the three existing copies of the Gutenberg Bible (the first book printed with movable type) and a large collection of books printed before 1501; numerous Civil War photographs; recordings of American folk music; and letters, papers, and drafts from many Presidents.

22 Name: Rayburn Building Location: Independence and 1st Street SW Building Stones: Exterior walls, Georgia White Cherokee marble and Vermont marble; perimeter base, New Hampshire pink granite; east and west courts and paving borders, pink granite (note large, regularly shaped pink feldspar crystals); inner court, base of Salisbury, North Carolina, pink granite with Indiana limestone above Remarks: William H. Livingston designed the building, which contains 169 suites for Congressmen. The nine-story building was complete in April 1965.