Art Institute of Chicago

Two bronze lions have guarded the Michigan Avenue steps since 1894, cast by the sculptor Edward Kemeys, and Chicagoans dress them in team helmets whenever a local side reaches a final. The building behind them went up in 1893 for the World's Columbian Exposition, the world's fair that briefly turned the city into a stage set of white plaster palaces, and the young institution, founded in 1879 as both a school and a gallery, moved in and stayed.

What people cross the country to see is a run of pictures that ended up here almost by an accident of timing, when Chicago's grain and railroad fortunes were buying French painting that Paris had not yet learned to want. Georges Seurat's 'A Sunday on La Grande Jatte', the huge park scene of Parisians stiff as chess pieces and built entirely from tiny dots of color, has hung here since 1924. A few rooms away is Edward Hopper's 'Nighthawks', the all-night diner on a deserted corner, painted in 1942 in the first winter after Pearl Harbor. And in the American galleries is Grant Wood's 'American Gothic', the pitchfork farmer and the woman beside him, a picture so parodied that people forget it is a small real painting on a board.

The newest part is the Modern Wing, a light-filled block by the Italian architect Renzo Piano that opened in 2009 and added a whole floor for twentieth-century and contemporary art. Its top galleries were built for painters like Cy Twombly and Gerhard Richter, lit through a canopy of aluminum blades that filters the flat Midwestern sky.