For my dad's birthday last year, Scott and I gave him a gift card (Groupon) for a tandem kayak experience on the Chicago River. Scott and I would be in one kayak, and my parents would be in the other. We redeemed it this weekend, and I can't say enough good things about the experience.
You are set up in a kayak with a life jacket and given a bit of brief instruction, and then you navigate your way through the middle of downtown Chicago on the river.
It was extremely scenic - I can't say enough good things about the view. It was also a workout, without seeming like a workout (so fun you can hardly tell your shoulders and arms are going to be screaming).
Every so often, our guide would stop us and tell us some information about the buildings we were passing or details about the area on the river. We first went East to Navy Pier, and then circled back to the Merchandise Mart. All in, a three mile loop.
I loved it. More city-scape photos coming later, but here is my favorite. Sailboats needed to pass to Lake Michigan, so the bridges had to be raised. Loved it.