1

Well...there are quite a few cities that have all of that.Munich and Berlin are two very obvious examples...

Safety depends far more on you,your preparation and behaviour than on which city you choose.

As for 'not too expensive'....can you be a bit more specific? How much can you spend per day?

2

Hello lucapal,

I am willing to spend up to 1000 euro in a 8 to 10 days. How about cologne? Have you been there before?

3

I have been to Cologne...personally I wasn't too impressed.

They do have a nice Christmas market though,and some good theatres/nightlife....

4

Which airports are feasible for you? Dresden(530'000) and Freiburg(230'000) come to my mind, but both have only small airports so you'll maybe have some extra travel time from Berlin or Frankfurt. Both towns have mountains nearby within a 30 minutes train ride and offer history and culture. The weather forecast predicts mild weather. The most probable areas for white Christmas are normally in the east(Berlin, Dresden(still 5 cm snow today but melting), sometimes also south east Regensburg, Passau). But nobody can guarantee.
Other options which are nearer to Frankfurt airport: Mainz(200'000), Würzburg(130'000), Heidelberg(150'000)
If you want to go the theater or opera please book in advance or at least buy some hours before the event. In my home town, the theater is quiet full in December.
The inhabitants in the () are just for orientation. I guess towns below 100'000 don't have enough events going on.

5

Here you have a list with all cities in Germany where you can find operas and theaters. If you look to go, you can easy find out a city with an airport. Performances in theaters are most if not all in German language. http://www.mezzosopranistin.de/Opernhausdt.html

6

Dresden :o)