Looks like we have to download some of the classics as Free DLC. Could have done without that seeing as my connection will probably take a week to do so!
http://www.eurogamer.net/articles/free-legends-dlc-at-forza-3-launch
The duo of maps accompanying them are the Benchmark High Speed Ring - a converted airfield and hangar (an "automotive playground") - and the Sidewinder Proving Grounds.
More interested in that