Avi My first visit to Germany was a combination of 3 reasons. First, I had a good friend who was at the time near the end of a 5-year posting to Berlin as head of the region (3 countries) for the Israeli Ministry of Tourism. Second was a group "seminar tour" of medieval Jewish and Christian history. Third was Mrs. Jo's promise to show me the best of Frankfurt. I started with Jo in Frankfurt - well-preserved historic center, especially the cathedral, and chock-full of Jewish history, especially the amazing excavation of the Jewish quarter. The tour began with Mainz's cathedral, Chagall windows, and ancient Roman relics. It continued with overnights in Cologne (awesome stained glass in the cathedral), Aachen, and Trier (superb Roman ruins) and ended with a scenic trip through the Mosel Valley mostly by boat and returned to Frankfurt. Highlights for me included two beautiful medieval mikvahs (ritual baths), churches, and Jewish cemetery, the Aachen cathedral where Charlemagne is buried and the super picturesque village of Monschau. Berlin has wonderful museums and lots of interesting WWII sites. Then I spent 2 nights in beautiful Dresden (good museums, lovely Frauenkirche painstakingly rebuilt piece by piece from the rubble after the WWII bombing raids, as is nearly all the historic center. From there I took the bus right to the Berlin airport.
My second, and probably final, visit was for Xmas markets.
PS - I had excellent weather on the first trip (3 weeks, June to early July), never too hot, only a little light rain. December was different of course, but never bitterly cold once I learned how to dress properly, but enough snow to last me for years to come.