Chicago is rich with various photo ops, with its wide variety of public sculpture and architecture as well as people on the street. Here, in my opinion, are the most popular spots you're likely to find shutterbugs snapping pictures in Chicago.
The "Chicago Picasso" (known as such because Pablo Picasso left it untitled) is one of the city's more famous landmarks. Located in Daley Plaza in the heart of Chicago's Loop, the Chicago Picasso is a classic photo opportunity, especially when it's dressed up like in this photo where it's sporting a Chicago Bears cap for the Bears' 2007 Super Bowl visit.
Also in Millennium Park, the Crown Fountain is a multimedia display featuring a variety of faces of Chicago citizens that are in continuous rotation. The addition of a water element and young and old splashing around at its base make for some great snapshots.