Thanks for the replies, everyone. They've given me lots of ideas (I really like the Loop tour idea)

A question -- can someone tell me about Millennium Park? I've been surfing around looking for information. Best I can tell is that it's a big open space with public art, theaters, and places to eat. Is there something I'm missing here? I won't have time to see a full fledged theater production and I'm not going to sit down to eat. Other than for the public art, what is there for me to do or see there?