Where to go in Europe?

What do you want to see? You are close to Belgium and France so would go to Alsace.

London, Vienna, Rome, Venice, Paris, Munich, Copenhagen, Birmingham, Nuremberg, Monaco, Budapest, Porto, Bratislava, Madrid, are all must see cities.

To the others who will read this thread: Birkenfeld is between Luxembourg and Frankfurt, to the south of the Middle Rhine and Lower Mosel valleys.

It is relatively "remote" in terms of transportation connections, so what you will be able to visit will depend on the number of days you are willing to stay out of Birkenfeld. If you only want to travel in short bursts of 1-4 days, with a car you can easily reach:
As day trips
- the Middle Rhine (stretch between Bingen and Boppard), but an overnight there would be nice
- the Mosel valley
- Trier (roman ruins, birthplace of Karl Marx)
- Luxembourg (surprisingly pretty city)
- Heidelberg
As longer trips
- Alsace (Strasbourg, Colmar...)
- Lorraine (Metz, Nancy)
- Bruges / Gent / Antwerpen, Belgium
- Paris even (take the high speed train from Saarbrucken)

As you can see the list is long...
Birkenfeld is also next to HAHN Airport which has low cost flights to many places in Europe - check it out!

Balso, I was about to suggest the Rhine and Mosel as well, and I always perk up when I see your name in threads. You have such comprehensive and helpful advice delivered in quite a pleasant way. OP, that corner of Germany (plus France and Luxembourg) is lovely, no need to go far in your short time frame.

also nailed it

sorry for auto correct. balso nailed it