One of the great things about St. Louis is all the free things here. The Science Center is one of them. There is a fee for parking if you don't park in the park and there are fees for the Omnimax, but the science center is free. It gets very busy with school tours, but that's because there are so many things for kids to do and see here. You can even walk across the highway in a pedestian overpass that links the science center to the old Planetarium--now science museum. Parking there is free.