“The Lingotto building, Turin, Italy, once housed a Fiat factory. Built between 1916 and 1923, the design had five floors, raw materials going in at the ground floor, and cars built on a line that went up through the building. Finished cars emerged at rooftop level, where there was a rooftop test track. It was the largest car factory in the world at the time. Le Corbusier called it “one of the most impressive sights in industry”, and “a guideline for town planning”.”
The rest is here: 1928: Rooftop Racetrack (Lingotto – Torino)