Overhyped public works don't need additional exposure from me. But here's some anyway. Millennium Park downtown is a lot of fun and worth a visit if you're a resident or a tourist. (Here's some newspaper reports and a photo essay). It's an odd contrast of extremely formal spaces with extremely modern, and sometimes overwhelming, sculpture and architecture. I particularly enjoy The Bean, also known as "Cloud Gate."
Reflection-spotting is also a popular pastime. Here, yours truly is the flash of light on the right.