Depends on what you like to do.
Things to do:
St. Louis Zoo (world class and it's free)
Art Museum (Free as well)
Science museum(also free) These three are all in Forest Park. If you come in the summer there is also the Muny Opera which is the largest outdoor theater in the US. Mostly musicals. There is also the St. Louis Wheel and the St. Louis Aquarium at Union Station downtown.
If you like to Gamble, there is Horshoe downtown and Casino Queen right across the river. Hollywood in Maryland Heights and Ameristar about 2 miles from there in St. Charles.
Missouri Boatanical Gardens (also known as Shaw's Garden)
City Museum for the kid in you
About 2 hours southwest of St. Louis are some really great float streams if you are into canoeing or tubing.
The arch and the museum at the base of the arch
Of course we have the Cardinals and our new soccer team.
The Old and New Cathedrals
And some other ideas:
https://www.busytourist.com/things-t...ouis-missouri/