My family loves to visit the st. louis zoo in the spring or fall. It's (amazingly) free, which makes it a great place to stop by for a bit while you're in the park for the day. Don't bother paying the money for parking. If you're willing to walk a few blocks you can park for free somewhere else in the park. They just finished a beautiful new huge bird exhibit which is great to see. Because it's free, you can spend your money on a ride on the train. Great place to visit, but does get very crowded on nice days in the spring and summer.
more