The Chicago Architecture Foundation , in the Santa Fe Building at 224 S Michigan Ave (tel 312/922-3432, ), runs a number of highly recommended tours throughout the city. Among these are two information-packed walking tours of the Loop, giving a friendly in-depth introduction to Chicago's buildings and history ($10 for 2hr, $15 for both tours). It also offers walking tours of Frank Lloyd Wright's buildings in Oak Park, Historic Pullman and other neighborhoods; bus tours of the Loop and Near North ($15; 2hr), Hyde Park and Frank Lloyd Wright's Robie House ($25; 3hr 30min). Perhaps the most popular of all are the excellent ninety-minute Chicago Architecture by Boat tours, which leave from Michigan Avenue and Lower Wacker Drive (May-Oct Mon-Sat 3 departures, Sun 2 trips; $21). Other sightseeing boat tours include those offered along the river by Mercury (tel 312/332-1368, ; $14) and Wendella (tel 312/337-1446) during the summer season; and Spirit of Chicago Harbor Cruises ($17; tel 312/836-7888), who continue year-round, sailing from Navy Pier. Shoreline Sightseeing Tours ($17 for architectural cruises, $10 for lake cruises; tel 312/222-9328, ) is another good option, with architectural river cruises as well as lake tours, a slightly different look at the architecture of Chicago.