Dangling school bus and salvaged jet.

City Museum

St. Louis, Missouri

Vast and purposely vague, City Museum is a labyrinthine funhouse of simulated caves, numberless cubbyholes, repurposed industrial debris, and floor chutes that plummet who-knows-where, including one that slides you down all ten stories of the building.

Its staff wears big "No Maps" buttons, and they mean it. Even with an experienced guide you can't possibly see it all, or remember all you've seen, in one visit.

And unlike House on the Rock -- the only other place that matches it for scale and chaos -- City Museum isn't out in the middle of nowhere. It's in the heart of one of America's largest cities.

"We want you to get lost," said J. Watson Scott, our chaperone and a long-time friend of the late Bob Cassilly, the guiding genius behind City Museum. "You can spend forever just looking at stuff in here."

"Just looking," however, is not really what Bob wanted of visitors. City Museum, with its deceptively bland name, was built primarily as the world's largest, craziest play-pit. Sure, the sedate can marvel at one-of-a-kind wonders such as Elvis Presley's travel trailer and the World's Largest Underpants. But Bob's heart was with the young and spry, and for them he designed a mazework of fake caves, tunnels, dizzying perches, and a Human Hamster Wheel.

Bob began building City Museum in 1996 inside an abandoned International Shoe Co. warehouse, out of discarded pieces of St. Louis (It officially opened Oct. 25, 1997). Thousands of abandoned soda bottles and safety deposit boxes were glued together into walls. The colossal door of a former bank vault was hauled in, and now leads into a hall of mirrors. Old cement mixer chutes were welded, end-to-end, into slides; one stretches from the third floor down to the lobby, where thousands of fabric scraps are nailed to the ceiling to make you feel like you're under the sea.

We walked past the World's Largest Pencil (a No. 2 that can actually write, 76 feet long) and a crew from Canada filming a dwarf engineer who was piloting the Museum's indoor train. We watched in awe as agile kids squirmed into subfloor tunnels designed for tiny beings.

From the caverns, with its passageways and fake show cave formations, you can look up a ten-story air shaft to the roof and see the pipes of the museum's 1924 Wurlitzer organ, salvaged from a Manhattan theater. A Bach fugue echoed across the cave's fake stalactites and dinosaur skulls amid excited, continual cries of "This way!" and "Over here!" Around one corner the "puking pig" -- an old boiler topped with an iron pig's head -- spewed water from its mouth every few minutes to the delighted shrieks of onlookers. Everyone snaps photos of everything with their phones.

Twisty shoe chutes ascend the air shaft.

Did we mention that City Museum also has gallery collections devoted to robots, the bugs of Missouri, opera posters, and doorknobs?

Outdoors, on the roof, you can ride a four-story Ferris wheel, or hang over the edge of the building in the driver's seat of an old yellow school bus. Kids, with weary parents in tow, scramble to lofty perches, the highest topped by a 20-foot-tall metal praying mantis.

Hovering over the museum's parking lot is MonstroCity, featuring two salvaged corporate jets balanced atop iron scaffolds. Visitors (again, mostly kids) crawl to them through wobbling aerial tubes of twisted rebar. Below, a log cabin formerly occupied by the son of Daniel Boone has been converted into a juice bar next to the ball pit.

The junk-and-rubble aesthetic of City Museum is the opposite of the typical soft-plastic sanitized PlayZone, and that's the point. "If it's not a little scary, it's not fun," said Scott, who assured us that casualties are rare, and that the museum always has band-aids and ice packs for those in need.

Bob wisely ran City Museum with his gut, freeing it from the vetoes of nervous corporate naysayers. His final creation was a giant indoor jungle gym made from hundreds of logs he found floating in the Mississippi River. Then, late in 2011, Bob died in an accident at another site as he was working to complete his follow-up project, "Cementland." His bulldozer rolled over on him.

Scott told us that dozens of other cities have sent observers to City Museum, wanting to build something similar. But none have. They've got the junk, but they don't have the driven creativity of Bob. "He was inspired by himself. This stuff was all in his mind," said Scott, who arranged for the museum's lone personal nod to its founder: a solitary photo of Bob in the lobby, framed on a wall built from thousands of bread factory baking pans. It goes unnoticed by nearly everyone. There's simply too much else to see.