The Petersen Automotive Museum in Los Angeles is already one of the biggest and best car museums in the world. And that's just the floors above ground.

In the three floors of the museum that are above ground there are, currently, exhibits on Porsche, lowriders, early Japanese cars and custom motorcycles, to name a few. But of the 400 or so cars and motorcycles in the museum, a little over half of them are stored underground in what is referred to as The Vault.

At first no one but museum staff was allowed in The Vault -- it was kind of dingy, a little dusty, and maybe there were shoppers left over from three decades ago when this place was an Orbach’s department store, still trying to remember where they’d parked. That changed gradually. First, special friends of the museum were shown around down below. Eventually informal tours were occasionally given, then given more often. In recent years the Vault tours were formalized. But now, what is officially called “The New World Tour in The Vault Presented by Hagerty,” sees a new paint job, a lot more lights, giant murals on the walls and no dust at all to speak of. It is shiny and ready for visitors.

We got a tour a couple days ago from Vault docent Peter Holman (no relation to Holman-Moody), who knows more about each car down there than you’re likely to find in a hundred google searches. The 250 Vault vehicles are divided into six different regions and provide what the museum promises is “…an immersive experience exploring the history of the automobile.” There’s a whole section on Porsches, for instance, one on French cars, one on hot rods, customs and roadsters, the latter including several AMBR winners, the America’s Most Beautiful Roadster award given each year at the Grand National Roadster Show. There are cars from the movies, including the Porsche 928 in which Tom Cruise learned to drive in Risky Business. There’s a row of armored limos that once carried heads of state, from Roosevelt and Eisenhower to Ferdinand Marcos, Saddam Hussein and even a Popemobile. It’s 60,000 square feet of wheeled wonderment.