From barn finds to Steve McQueen, the million-dollar cars selling at Pebble Beach this weekend

Starting Friday, more than $200 million' worth of classic and rare automobiles will go under the hammer at the auctions surrounding the Pebble Beach Concours d'Elegance in California, with more than 70 of those expected to fetch at least $1 million. Even amid a booming market for old cars, there are a few that stand out -- including one that was once ditched on the side of a California freeway, and another that sat in a shed for nearly 40 years which could break the auction record of $16.4 million.

While the Pebble Beach show itself will draw 15,000 visitors on Sunday, the plethora of auctions around the event in Monterey, Calif., have become even more of a spectator event. Among the gawkers will be wealthy buyers hunting not just a jalopy they can boast about, but a place to invest their money that could pay off big. Hagarty's Insurance, which tracks collector-car prices, says its index of "blue-chip" collector vehicles has risen 9 percent this year to a record high -- a greater return than almost any other investment class. The world will always have more gold and stocks, but there won't be any more 1965 Ferraris.

From the hundreds of vehicles that will be offered this weekend, here's five that will get much of the attention and some of the highest bids:

1936 Mercedes-Benz 540 K Special Roadster

The star of the weekend, this massive, supercharged Mercedes-Benz was owned by Baroness Gisela von Krieger, one of the last members of German aristocracy and a socialite once named among the world's most beautiful in pre-war Paris. After the war, a newly reclusive von Krieger moved to New York, and later Connecticut, bringing her car with her. When her brother died in Europe in 1959, von Krieger stayed, leaving her car in the shed of a Connecticut inn for safekeeping.

This isn't just any Mercedes-Benz roadster, but one of a handful of copies of the finest cars the company built before World War II; the von Kriegers ordered it with a custom body, dash and even a pushbutton radio, a rarity in the era. Despite entreaties from several collectors and Mercedes-Benz itself, von Krieger died in 1989 without ever selling the car, despite not seeing it for more than three decades.

With no heirs, von Krieger's car fell into a legal abyss; only when a lawyer contacted auctioneer David Gooding in 1991 about an "old, black two-seat Mercedes" did the mystery start to unfold. With a few more details, Gooding flew across the country to inspect it, and found the Roadster almost as von Krieger had parked it in the '50s -- her spent cigarettes still in the ashtray.

After a spare-no-expense restoration by owner Lee Harrington, the 540 K Special has won several prizes over the past few years, including a best-in-class at Pebble Beach. Estimates put the car's value at a minimum of $10 million -- and given the passion for having one of the rarest vehicles in the world, it could sell for far more.

1935 Duesenberg Model JN Convertible Coupe owned by Clark Gable

Just because a movie star owns a car doesn't make it collectible, but there are cases where stardom and a love of cars combine to create the kind of unique vehicles collectors chase. That's the case with this 1935 straight-8 Duesenberg that was Clark Gable's personal car, one he had thoroughly restyled and customized into a roadster, and used to pursue Carole Lombard. From their first date to her death in a plane crash in 1942, the Dusenberg was Gable's ride of choice.