Fields museum in Chicago is one of the best museums- with many permanent exhibitions - very interesting- and many interesting temporary exhibitions several times a year. Chances are that even if you went to see it couple of times, there is still something interesting to discover. You will need at least a whole day - so it is nice that actually you can have lunch on-site. (Corner Bakery is my favorite)- or you can pack a snack and stay at the tables at the food court.
nice and interesting way to spend a day.
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