Bob Cassilly’s vision lives on in every worker and artist in this museum.

“Pretty much the same crew since the beginning, even with Bob. It’s a tight crew,” Erwin said. “We have a stone worker pretty much our people can work in Metal, plaster anything we throw at them they can come up with.”

Everything here has a story.

“There are some really cool things, like upstairs with the Edward Bates school, I once saw where a grandparent walked through and realized that’s where he went to school,” Erwin said.

One minute you could be inside a gorgeous sculpture of a giant whale; the next you’re crawling through a cave. You might start off in a treehouse, hop down a slide, and wind up in a massive, adult-sized ball pit. Or you can be admiring a room full of priceless opera posters and accidentally wander into an aquarium.

In an attempt to understand the enigma that is City Museum, I set up an interview and tour with Richard Callow. Callow is listed as the media contact on City Museum’s website, but he’s more like the story keeper of the place, and has been since the founder—famed sculptor and artist Bob Cassilly—died in an accident in 2011.

City Museum is housed in a sprawling, 10-story, 600,000-square-foot former shoe warehouse. A school bus dangles from the building’s roof. The ultimate jungle gym extends from the windows.

To assemble our first annual list of the World’s 50 Coolest Places, TIME for Kids sought input from trusted experts—kids.

Bob Cassilly’s City Museum at St. Louis is Alice-in-Wonderland, down-the-rabbit-hole surreal, going against the logical patterns and enforced pauses that define the ordered grid of a city.

The sound of children playing is the first thing you hear as you approach the gates, painting the air with the joy of play. But it’s misleading: The grown-ups who belong to them (and the ones who don’t) are at play, too. They traverse cage-like ladders to get to airplanes atop metal structures and meander across walkways and ramps built four stories in the air.

This is City Museum in downtown St. Louis, where anarchy is – sometimes quite literally – in the air.

Here, the rules that govern the city and its inhabitants are stripped away. The layout and structure itself is as if Dalí and Gaudí dropped acid in a salvage yard and miraculously managed to create a structure. There is only one directional sign at the front entrance, and the staffers at the ticket counter will tell you quite firmly that there are no maps.

If you gave Dr. Seuss and M.C. Escher free reign over an old shoe factory and told them to build the world’s craziest jungle gym, you’d get the City Museum in St. Louis Missouri.

This isn’t your typical museum. Very little is “for display only,” in fact touching is highly encouraged. The environment you interact with itself is the museum. You climb, crawl, scoot, slide, and ride all the exhibits.

It’s something you may not have ever noticed: a hippo sitting high atop Washington Avenue! But Emily Dittmer did, and she wonders about it every time she walks by.