Chicago boasts 29 miles of shoreline and 15 miles of beaches along Lake Michigan, which warms up for swimming in July and August. Our picks: Ohio Street Beach, small, among the least-crowded and near Navy Pier; and North Avenue Beach with bustling crowds, a retro beach house that resembles an ocean liner, and proximity to Lincoln Park and the zoo. The main park office is located at 541 N. Fairbanks, and provides plenty of information on things to do on the lake.