I've booked a trip to Germany next month, May 13 - 29th. I've already split up my time betwen three cities, but haven't decided on what to do each each city. I'm not a drinker, but and avid photographer. So I prefer scenic "postcard" tours rather than wine/dine/arts. I'm just looking for day tours, since I'm using my Marriott points for the hotel stays in each city.

In Berlin I'm also looking for fun things to do in the city, since I'll be there the longest and won't need to cram in tours. I would like to see some castles in Frankfurt, and at least once concentration camp near Munich or Berlin.

My schedule is:

May 13 Arrive Frankfurt - May 16 FRA to Munich
May 16 Munich - May 20 Munich to Berlin
May 28 Berlin to Frankfurt - May 29 Frankfurt back to USA

Full days available for tours are:
Frankfurt 14-15
Munich 17-19
Berlin 21 - 27

In Frankfurt a day tour on the Rhine River was sounding nice, and I'm trying to decide between a day tour of Wurzburg, Rotherburg or Heidelberg. I'm leaning towards Heidelberg.

I haven't had time to research Munich or Berlin yet, so I'm wide open on pointers for things to do. Thanks in advance!