My father is a bit of a WWII history buff, so my brothers and I are chipping in to send him on vacation in Germany next summer. What I'd like to know is, what are the best World War II sites to visit in Germany? I know about Auschwitz and Checkpoint Charlie in Berlin, are there any others that he shouldn't miss? Which attractions are good for someone with reduced mobility, as he's getting quite old and can't walk for long distances? If anyone has any advice or experience to share it would be very helpful.