What do you like to do? The zoo, art museum and science museum in Forest Park are all free, except for a few special exhibits and things like the zoo train and children's zoo. City museum is a place for your inner child to run wild. Top of the Arch, Old and New Cathedrals, Anheuser-Busch-InBev brewery tour. Cardinals or Blues games when they are in town. Lots of good/great places to eat. Too many to list here and depends on what you like. Steaks, BBQ, Italian. Depending on the weather, the Missouri Botanical Garden. Tale a carriage ride downtown. Several casinos. Quite a few strip clubs within a short drive. (Go over the bridge. Strip clubs in St. Louis suck.). Delmar Loop. Ted Drews.
http://explorestlouis.com/visit-expl...o-in-st-louis/
That should fill up a weekend.