The St. Louis Zoo is a award wining quality zoo. It is home to many animals shown in natural settings, from the great apes, to the elephants, to the penguins. To top it off the admission to the zoo is FREE! 

 In fact most of the attractions in Forest Park; a urban park  larger than Central Park in NYC. are Free. Plan on spending at the very least one entire day just in Forest Park. Better yet spend more than one day. You will be happy you did.