I've done it before. It is beyond awesome.
But, if you are in Germany, there is a HUGE motor museum in Mannheim. (This was easily the best experience of my whole trip.
http://www.technik-museum.de/english
Looks like an aeroplane museum, which is it's main feature. But the cars here are beyond anything you have ever dreamed of. Awesome classic, there's even a classic ferrari display.
Give yourself a full day.
Check this photo for example. U can see in the background there is another level of cars. (Sorry, I'm getting excited just thinking about it) They had a delorean!!!
