In 1940, General Motors wanted to wow the American public with its vision of the future. To showcase those ideas, it designed one of the strangest automobiles you’ll ever see. The GM Futurliner resembles an RV. It weighs 30,000 pounds, has a top speed of 38 mph, and is as tall as a two-story house. Now, one of the nine Futurliners still in existence is going up for auction, and it’s expected to fetch a hefty sum.

The automaker used the funky ride as part of a traveling show called the "Parade of Progress.” At towns and cities around the U.S., GM employees would show off novel inventions like the jet engine, radar, television, and microwave. For the tour that started at the 1939 New York World’s Fair, GM created the Futurliner, which carried animated exhibits like “Miracles of Heat and Cold.” When it was time to hit the road again, the exhibits folded back into the vehicle.

The 1950 Futurliner in question is currently part of Ron Pratte’s enormous collection of mostly American automobiles and memorabilia, which includes historically significant vehicles like the Shelby Super Snake and first production Ford Thunderbird. Pratte is selling his entire collection at the Barret-Jackson Scottsdale auction in January 2015, and he’s not telling anyone why.

Whatever the answer is to that mystery, the Futurliner is a remarkable vehicle. “I remember thinking, ‘What the heck is that?’” says Craig Jackson, CEO of Barrett-Jackson auctions, which originally sold the car to Pratte in 2006. “I was intrigued right away.” That’s means a lot coming from a man whose company brokered the sale of the original George Barris Batmobile (for $4.2 million), and a 1966 Shelby Cobra Super Snake (for $5.5 million).

The Futurliner was designed by Harley Earl, one of the shining minds of the United States’ greatest design eras — he took inspiration from old streamliner trains. “This was a major auto manufacturer with a special place in time,” Jackson says. Only 12 examples of the vehicle were built, and the last Parade of Progress was cancelled in 1956.

Pratte bought this Futurliner in 2006 for $4.1 million, after its Canadian owners brought it down on an oversized flatbed for sale through Barrett-Jackson. The auto industry and the country as a whole have been through a lot of turmoil since then, but Jackson says the once futuristic vehicle is as relevant as ever. “Car makers had their troubles back in ’08 and ’09 … but the world still copies us as soon as we innovate. This was an era where we were the manufacturers of the world.”