"First of all, you have the salt, which corrodes aluminum, which corrodes metal. Then it's so hard, even though it flakes off on the outside, you can't nail anything into it. So we had to ramset everything in.

"Here's another thing: It's always moving down there. So we can't build any wall up to the ceiling because the ceiling is always pushing down, and the floors are always heaving up.

"No one who worked on the project had ever worked in that kind of environment before. Nobody knew how to do that, so that just led to all kinds of challenges and setbacks."

For instance: How to move waste from the restrooms to the surface? (Lots of pumps and back-up systems do the dirty work.)

And how to keep visitors from veering into unsafe areas or getting lost? (Walls were built to discourage wandering.)

I didn't wander off any beaten path, but I did lose myself in contemplation over Batman.

Standing in front of the costume George Clooney wore as the Caped Crusader in the 1997 movie "Batman & Robin," I marveled at the six-pack abs sculpted into the rubber suit. It even had nipples. And the Bat boots?

My, my, George has small feet.

Next I stood in awe in front of the Mr. Freeze costume, a silvery monstrosity worn by Arnold Schwarzenegger in the same movie.

My, my, Arnold has an enormous, uh, codpiece.

Yes, this is still a story about the salt museum. And yes, there are Hollywood costumes displayed here. They're kind of a tease, a glimpse of the countless Hollywood treasures stored not far away in Underground Vaults, with 50 acres that are off-limits to the general public, a real bummer for Hollywood buffs like me.

Company president Lee Spence once called the storage company "a kind of Noah's Ark, without the animals."

Sony Pictures, 20th Century Fox and Warner Bros. all hide things at Underground Vaults. It's a veritable Fort Knox safe from tornadoes, floods, earthquakes and all manner of mischief and mayhem, where the 68-degree temperature and 45-percent humidity are ideal for preserving paper and film.

Turns out those are comfortable working conditions, too, for anyone who's not weirded out by spending hours underground. Employees wear shorts at work on even the coldest days of winter.

The company stores millions of boxes full of paper and data - oil and gas company leases and maps, insurance policies, architectural blueprints, medical files, tax records, historic New York newspapers reporting Abraham Lincoln's assassination.

Secret government documents are locked up here. (The truth about Area 51, perhaps?) Everything is electronically catalogued and bar-coded so it can be easily found.

"What people need to realize is our clients trust us to secure their information. They trust us to make sure that we're not a tourist facility," company vice president Jeff Ollenburger said.

"Where there are occasions where we might bring people through for an official tour, it's very rare that we do that. That's one of the reasons we support the museum, and we've tried to create a small exhibit over there about what we do."

The Underground Vaults folks are loathe to reveal specifics about their clients. But over the years they have shared that they are the keepers of such historic movies as "Ben-Hur" and "Star Wars," old silent movies, every episode of "M*A*S*H" and the original film negative of "The Wizard of Oz."

Harry Potter and Scooby-Doo live here, too.