One of our favorite things about Chicago is the architecture. We think one of the best ways to view it is from another Chicago triumph -- the river! There are many incredible companies to choose from, but we would suggest the Architecture Foundation first.
There are three museums on Museum Campus that we equally recommend: Shedd Aquarium, the Field Museum of Natural History, and the Planetarium. If nothing else, head to the Planetarium for one of the best views of the city.
If you are looking for a more active way to explore the river, we recommend Urban Kayaks. Choose either a single or tandem kayak and see the river at your own pace.
Don't be alarmed by the fighter-jets flying over the city during the weekend: Saturday & Sunday will be the Chicago Air and Water Show! While visible from nearly anywhere along Lake Michigan, it is focused at the North Avenue Beach. Visit the website for the schedule.