http://www.gp-suisse.ch/

It's more of a parade than a race, but a great collection of cars and bikes taking part :

http://www.gp-suisse.ch/csv/meldeliste2012.pdf

There's also fly-pasts throughout the day, including a P51 mustang

There was a retro event in Cologny in 2003 when I was living near by. From memory one of the sponsors were Bentley and the pace cars were Arnages. Fortunately they are the historics were being driven as intended, with a decent amount of slip round the temporary chicane were I was standing.

Motorsport as it was intended. A lovely sunny weekend, close access to the cars and a stand selling rosé with good food nearby.