LOS ANGELES — The Petersen Automotive Museum is a must-see for any auto enthusiast who happens to visit Los Angeles. Situated on the corner of Fairfax and Wilshire in a building that was once a department store, the museum was founded in 1994 by magazine publisher Robert E. Petersen and his wife, Margie.

Petersen’s publishing empire, which he sold in 1996 for $450 million, included Hot Rod, Motor Trend, Car Craft, Sports Car Graphic, Motorcyclist, Mountain Biker, Photographic and a few others.

The museum’s ground floor has a number of dioramas in which historic vehicles are set, and the second floor houses both permanent and rotating displays, but it’s the “vault,” previously closed, that everyone wants to see.

The vault is the underground garage that houses much of the 410-vehicle collection that is not on display in the upper floors of the museum. Guided tours are limited to 10 people at a time and cost $25 on top of the museum admission fee. No photographs are allowed.

I visited the museum with an old high-school buddy and his brother in late January, and we were excited to see the vault. Notable vehicles include Jayne Mansfield’s pink Lincoln, the Magnum P.I. Ferrari, Audrey Hepburn’s Imperial, Saddam Hussein’s Mercedes and a Cadillac owned by Clark Gable and Carole Lombard. But the vault holds dozens more cars. One of almost every early Porsche is there, and ditto for Ferrari.

A priceless 1952 Ferrari 212/225 Barchetta, originally a gift from Enzo Ferrari to Henry Ford, caught my attention. Painted black, with whitewall tires on chrome wire wheels, the diminutive little Ferrari is the last non-racing Ferrari bodied by Touring, an Italian coachworks. It is completely original and has fewer than 13,000 miles. Ford stylists admired the car, and the 1955 Thunderbird bears several design cues that were influenced by the Ferrari.

The heart-stopper, however, is the massive 1925 Rolls-Royce Phantom with a body by Jonckheere. Known affectionately as the Round Door Rolls, the car was given a new body in 1935 by Belgian Jonckheere company. Jonckheere, according to Octane magazine, was founded in 1881 to build horse-drawn carriages. In 1934, the company was building streamlined, single-deck buses. The inspiration for the Rolls, with its long, sweeping tail and round doors, is unknown. It is 22 feet long and weighs 7,200 pounds, according to Octane. The front seats folded back to make a double bed, and the famous Rolls-Royce grille was raked back for an aerodynamic look.

The car was discovered in a New Jersey junkyard in 1950 and, painted gold, spent several years as part of an auto exhibit. Petersen acquired the car in 2001 from a Japanese collector and had the car restored by Tired Iron Works in Monrovia, Calif. The completed car won the Lucius Beebe Trophy at Pebble Beach in 2005. Seeing it sit quietly in the darkened parking garage, recently home from a trip to England, was like eyeing the Hope diamond sitting in a dime store jewelry case. Being able to stand next to the car was worth the $25.

Peter Mullin, new chairman, has announced plans to revitalize the museum building and its collection, in time for the 20th anniversary next year. The Orange County Register reports the building’s exterior will get a major redesign and future exhibits will highlight more European cars and technological breakthroughs.