One of the rarest Ferraris in existence has become the most expensive car ever sold at auction. Price tag: £25 million, or about $36 million. Adding to its rarity, only four of the 1957 Ferrari 335 S Spider Scaglietti were ever made. Auction house Artcurial Motorcars put the vehicle on the block during its annual Retromobile sale in Paris. Auctioneers there compared it to Picasso's paintings or Rodin sculptures. Ferrari's workshop equipped the model with a 4.1-litre V12 engine, giving it a massive 400 horsepower and enabling it to reach a top speed of 190 miles per hour—unheard of at the time. The fact that it was driven by some of the world's best drivers—including British Formula 1 champions Mike Hawthorne and Stirling Moss—only increased the price. Here's a closer look.