A little bump here, but reading through the thread I just needed to. Really interesting, and sad, to see pictures of the long forgotten race tracks.
Speedhunters have had trips to quite a few lost tracks including the Südschleife, Sitges, Clermont Ferrand and the old Monza banking among many others. Bear in mind that there's also some other "none-lost" tracks on the 4 pages in the link.
http://www.speedhunters.com/category...templeofspeed/
Interesting read and great pictures!