Non-touristy things to do in Chicago?

I'm traveling to Chicago as a tag-a-long with my hubby for a work trip the second week of April. He's working all day, so I get to explore on my own! Its been years since I've visited and I'm not interested in the TripAdvisor list of The Bean, the Willis Tower (was still the Sears Tower last time I was there), the river walk, the pier, etc. What are some off-beat things you folks would recommend for a lone traveler to enjoy over 3 or 4 days in April.