Deutschlandring
This 10 km track, located near Dresden, was built in 1939 with the aim
of catering for 1 million spectators, and with parking for 350,000 cars. It
featured a 1.06 mile start-finish straight, with some 200m of it 25m wide.
The track layout itself was completed, but supposedly the pits and
grandstands weren't. It was planned to hold the 1940 German GP at the track,
but the war intervened, and racing did not resume at the track after war.
Or, at least, official racing - locals or people in the know used to race
around at high speed until the police installed speed cameras and speed
bumps.