A mini fossil museum exists within the lobby of the Park Hyatt in Chicago, just off Michigan Avenue. I'm guessing not too many people know about it unless they're guests at the hotel. It's a wonderful display of very large Moroccan trilobites, ammonites and various other fossils from around the world. It is free, of course, because it's in the lobby and a nice diversion if you're ever in the area. Another added bonus is it's open 24 hours.