iO Theater (formerly ImprovOlympic) at Pipers Alley on North Wells is the second of Chicago's legendary improv comedy institutions, the training ground for Tina Fey, Mike Myers, and dozens of other performers who went on to build careers in American comedy. Where Second City performs scripted sketch shows with improvised segments, iO specializes in long-form improvisation — the Harold format developed by Del Close and Charna Halpern.
Multiple shows run every night of the week; the most expensive ticket costs considerably less than a commercial theatre seat. The bar at the front of the house is open to the public without a show ticket and is a useful place to eat before a performance. North Wells at North Avenue.