Largest rooftop automobile track

Fiat’s Lingotto automobile factory in Turin, Italy, was constructed with a roof-top oval test track, measuring 0.621 miles (1 km). Two straight tracks of over 400 m in length and 15 m in width were connected by two banked curves, along which cars sped at up to 90 km/h. Designed by Giacomo Mattè Trucco and opened in 1923, the track still survives as of December 2013, although the building is now used as an entertainment, shopping and hotel complex.