4802 N. Broadway, 773-878-5552 or greenmilljazz.com
Type of music: Jazz
History: With roots as a roadhouse and a later phase as a mob hangout during Al Capone's heyday, the Green Mill is both a cultural and sonic gem, restored to its Prohibition-era speakeasy glory in the late 1980s after barely surviving the 1970s.
Crowd: Sophisticated and stylish, with weekend shows enticing first-timers out to impress dates with their taste in music and atmosphere.
Behavior: The unwritten rule, apart from ordering cocktails, is to remain relatively hushed. And jazzheads tend to be more inclined to pay attention than their rock brethren.