When it opened in 1923, Fiat’s Lingotto Building was the largest car factory in the world. It featured an entirely unique design where raw materials entered on the ground floor, and the cars were constructed on an assembly line which climbed through the building. Eventually, the finished cars emerged onto the roof – directly onto a rooftop test track! The factory sadly closed in 1982, and has since become a multi-use complex featuring a theatre, concert halls, and a Meridien hotel. You can read more about the wonderful Lingotto Building at Wikipedia. Thanks to Oliver Dueck and A.