The Museum of Science and Industry is a great place to visit, with a few caveats: If you go on a Saturday or Sunday, expect to be mobbed by children and adults.  If you go during the school year, expect to be mobbed by school groups.  If you are interested in a special exhibition (in recent years, artifacts from the Titanic and the Body Worlds), be sure to get tickets well in advance.  
Beyond the special exhibits, the permanent exhibits like the U-505 submarine, the coal mine, and the Pioneer Zephyr all make the Museum of Science and Industry worth the trip.  Be sure to save enough time to see a movie in the Omnimax theatre.  There is plenty of parking in the underground garage in front of the museum.   
                        
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