Nothing plan except to go walk around Forrest Park. It supposedly to be bigger than Central Park. Not sure. It even has 2 small golf courses in the park. Another interesting fact, it was the place where St Louis had its World Fair back in 1904. There was quite a few attractions here. A good place to start is the Visitor Center where they can give you recommended self guided walking tour in the park. The scenary of the park at this time of the year was pretty good. Definitely don't miss this place.
I walked around the park for 2 hours before started to head back to Kansas City. It was totally worth 7 hrs I made from KC! Highly recommended: the Gateway Arch.