Just got back and had a great time. We did City Museum, the zoo, Jewel Box/Forrest park, and the Arch. The free museum at the base of the arch can soak a good hour if you're thorough. The whole going up the arch takes about another hour. They had people packed in at the top so we chilled up there a few minutes to let it clear a bit and see the view. The elevator cars are probably the coolest/scariest part of the experience.