For a non-food related adventure, I highly recommend kayaking the river.
kayaks by
tsearcher2011, on Flickr
That photo is of a group tour which I haven't done. I think it's more fun just to go with some friends. There's two places that I know of that rent kayaks, google will bring you to them. They give you a 5 minute lesson if you've never kayaked before. It's super easy. Way easier than a canoe or rowboat. The activity itself is fun and you'll get a new view of the city.
The only downside is the river can be smelly and you'll get wet. You can also kayak the lake, but when I went to do that, people were just staying in one place and getting flipped over by the waves.