When it was built in the 1920s in Turin, Italy, the Fiat factory was designed with a racetrack on the top of the building, both for car testing purposes and for racing.
The factory’s best-known symbol is the test track, which is a superb piece of design modeling, and construction that occupies the whole roof surface of the workshops. Two 443 meters straights, joined by parabolic bends, form a continuous track for testing the cars.
Originally, as soon as the cars left the assembly lines they could flow directly upward to the test track through the snail-shaped ramps completing the whole processing cycle inside the factory. Moreover, these spiraling ramps inside the building allowed the cars to be driven back down and into showrooms.
The track was a little over 1/2 mile long. Many more views at Rare Historical Photos. (via @laxgani)