Chicago natives may disagree (or agree) but for an amazing Chicago deep dish pizza experience go to Lou Malnati's. I also appreciate that while it is a chain, you will only find it in IL. You're welcome.
Visit the Signature Lounge on the 95th floor of the Willis Tower. You will be able to see all the way to Iowa (not really), but the views are amazing and the drinks are even better.
Baseball fan or not, anyone and everyone can appreciate Wrigley Field. This iconic field was built in 1914 and has an addictive atmosphere that will turn you into a cubs fan, if only for 24 hours. The field is also surrounded by great bars and restaurants. If it is baseball season get tickets in the cheap seats and enjoy. Wrigley hosts concerts and other events throughout the year.