St. Louis, Missouri
The City Museum in St. Louis is a giant playground full of old building materials that have been repurposed. Opening up in 1997, and having 11 floors full of fun and exploring, the City Museum is not a sight you would want to miss at all! Open daily, this is the one museum I have ever heard of that encourages noise and activity around, and even on, their art. Once you get into the building, you are on your own to explore. They give warnings that there is no map, and if you like you can purchase knee pads. There is also a tip that there is a 10 story slide that can be found in the caves, so remember that when you get the chance to stop in. There is even a giant outdoor playground to go play on once you get done being inside. Definitely a place every child and adult must get the chance to go and play.