If you only get one stop alone in St. Louis, make it Forest Park (free, 1,300 acres, 30+ miles of paths). Next on our list are Saint Louis Zoo (free admission, open daily 9am-4pm) and Saint Louis Science Center (always free entry, closed Tuesdays); the other three, down to Old Courthouse, are below with where to book.
free entry, no ticket, new exhibits
free, open sunrise to 10pm daily
tram to the top, adults $15-$19
always free entry, closed Tuesdays
free admission, open daily 9am-4pm
free, 1,300 acres, 30+ miles of paths