There are several competing boat tours you can take when you visit Chicago. Most of them originate from Navy Pier these days, although there are also some that start from under the Michigan Ave. bridge.
These guys have been around since 1939 and do it right. They tell you a lot of interesting Chicago history as you tour the downtown lakefront in the boat.
I remember taking this tour as a kid and I'm sure it would still be fun. Chicago's lakefront is beautiful and has a fascinating history so if you want to play tourist, this is a good choice.
http://www.shorelinesightseeing.com/
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