This may sound sick, but try and find an old KZ Concentration camp memorial to visit. Really sobering. We went to one near Hamburg, Neuengamme I think it was called, and I'd highly recommend it. Very, very moving.
Berlin is definitely worth seeing too, even if you have to jump on a train or plane to go see it. It's a beautiful city, just watch out for the naked people in the city parks at lunchtime.
Other than that, remember to keep right on the AutoBahn unless you're passing, and if you are passing don't do it on the inside. Those cars come up in your rear view mirror pretty quickly even when you're doing 170 or so in your Toyota Aygo...