On New Year's Day, I have a long (6 hour) layover at Chicago O'Hare. Since I've never been to Chicago, I'm wondering if that's enough time to get out of the airport and go see a bit of the city. What are your thoughts? I arrive around 2:00 and would need to be back at the airport at 8:30. Since it's New Year's Day, I'm also not sure what would be open.