Basically, you almost can't go wrong in Germany. There's one charming town or village after another.

If you would like to see photos of some of the places mentioned in this thread, feel free to check out our photo albums from our last three trips (2005, 2006 and 2007):

http://travel.webshots.com/album/561038806XxDcvw

http://travel.webshots.com/album/554510509SyxotU

http://travel.webshots.com/album/354616542PMkPVQ

My wife and I have been going back to Germany since our days stationed in Stuttgart in 1970/71 with the US Army. We are now both in our 60s. We have made Germany trips in the summer, winter and fall. We have been to over 6 Christmas markets in 6 years. We have probably explored more of this country than the US.

You will not go wrong with the Mosel. We enjoy that area more than the Rhine. You can see the Rhine on the way. We stayed a few years ago in Cochem (1997) at the Altes Thorndecke. Great place and nice area to explore the Mosel. With only 4 days and some jet lag this would probably work for you.

Another thought would be to go to Rothenburg. Stay there and explore the Romantic Road, Nuremburg and that area. Rothenburg itself, while touristy, is worth two days.

Either way, you cannot go wrong. Germany is one of our favorite places.