Despite how young the Park is (2006, 4 years after it was supposed to open), it appears to have become a symbol of Chicago, as the natives have told me.
It's a quick, free tourist thing. It's generally busy (there were three wedding photo shoots while we were there) but its a must.
Lay/sit down for a photo at your own risk. It's a cool photo opp but its still laying down on a sidewalk. Ew