Ballpark Village is located right next to Busch Stadium and has multiple different bars and restaurants inside. There is even a rooftop terrace overlooking the stadium. It's a great place to watch away games or home games you can't make it to!
The St. Louis Zoo is consistently chosen as the #1 zoo in America and is truly one of the best zoos in the world. The St. Louis Zoo's primary focus is education and conservation - the animals are well-cared for and they are happy and active. Best of all, the St. Louis Zoo is completely FREE! (but parking is an additional $15 and some specific attractions - such as the Sea Lion Show or Stingray Encounter - are a few dollars extra).
The Arch is probably the thing people think of most when they think of St. Louis. The museum is a great place to learn about the history of St. Louis and of the Arch. Even if you're not able to visit the museum, this is a can't-miss landmark when visiting the Lou.