The National Gallery of Art is one of the finest art museums in the United States and, remarkably, charges no admission. The West Building, a neoclassical John Russell Pope design completed in 1941, holds European painting and sculpture from the Middle Ages through the 19th century, with outstanding collections of Dutch, Flemish, Italian, and French painting. The East Building, I.M. Pei's dramatic angular addition from 1978, holds the modern and contemporary collection.
Allow a full day if you intend to see both. The collection includes work by Raphael, Vermeer, El Greco, Monet, Picasso, Matisse, and Rothko — among hundreds of others. The East Building's entrance hall, with its soaring triangular atrium and Alexander Calder mobile, is itself worth visiting. The Cascade Café in the basement concourse is a good lunch option.