The 11417 meters (7.1 mile) long public roads in the wooded countryside to the west of Stuttgart were used as the temporary race track Solitude between 1924 and 1965.
After WW II, the Solitude featured several German Motorcycle GPs and non-championship F1 races which attracted huge crowds of up to half a million people!
Legendary pilots like Geoff Duke, John Surtees, Wolfgang Graf Berghe von Trips, Dan Gurney, Jack Brabham or Jim Clark competed there.
In addition, the Solitude was used by Mercedes-Benz and Porsche (both companies being based in Stuttgart) and NSU (the world's largest motorcycle factory in the 1950s) as a test track.
The last race on the Solitude circuit was held in 1965 due to several reasons, especially the questionable safety for pilots and spectators, as there are almost no run-off areas, but a lot of trees next to the track. And between the trees and on the hills sides, the spectators were placed.