Over 20 years ago, as a teen, I went to St. Louis with my mom who was attending an art teachers' conference. I think the City Museum was almost ready to open to the public, and the conference arranged to let us all in one night.
The place is nuts. It's even nuttier with 600+ art teachers getting their minds blown all at once.
Fast forward to five years ago, when I went back, this time with my own kids. I tried to prepare my wife, but it's hard to convey in words just how much _everything_ there is. Of course they had added even more over the years.
We did a lot stuff in St. Louis during that trip, but the City Museum is the thing my family still talks about.