What would you do? Recommend a city for 3-4 days via Frankfurt please!
 

What would you do? I have 3-4 days to enjoy somewhere after landing in Frankfurt. What's the best bang for my buck, exclude Paris and Central/South Germany please, as I've travelled them already.

So far i'm leaning towards Frankfurt > Dublin on Lufthansa for $145 Canadian return. Looks like the best value so far...decent timing and cheap...

RyanAir has flights out of Hahn for ~$40 euros but between transportation and time wasted i think i'm going to ignore it.

Have you been to Italy?

No, only been to Paris, South of France (Nice/Cannes), London and South of Germany (Frankfurt, Heidelberg etc)

However I'll be alone and my girlfriend did mention that she'd prefer that i save Prague and Italy for us to enjoy together ;)...but there are many cities of course! Is Zurich or Geneva interesting?

From Frankfurt, I'd suggest you just take smaller local trips or go to one place that interests you. Colmar comes to mind as a very charming place everyone likes. Otherwise, I'd head north along the Rhein and then south along the Mosel, stopping wherever your fancy takes you. There are lots of lovely villages along that route. Good luck.

If the Rhein and Mosel are in the area you consider to be central or south Germany and you don't want to go there, you could try a visit to the little finger of Holland that pokes southward toward Germany, including two of my favorite cities, Maastricht and a lovely village called Valkenburg. Good luck.

I am not sure if you visited the palaces of Ludwig II (near Fussen) and at Herrnchimsee, and I do not know if you want to visit only big cities, or..
I would recommend some options:

1- Salzburg, visit Hernnchimsee Palace, Innsruck
2- Palaces near Fussen and Oberamergau
3 - the small towns around Konstanz Lake (Boden See), including Lindau, Meersburg and Mainau Island (it is a huge and superb park of flowers)
4- Zurich, Stein am Reihn, Rhinne Falls (there are not far one from other).
From Zurich you can also visit Lucerne - beautiful! Also, from Lucern - a trip to Mt. Pilatus
You can travel between all of them by train
5- Did you visit Munchen? It has a lot to offer!
6- You can go by train or by plane to Berlin
7 - Amsterdam

Oh, there are so many places to visit!!!
I am sure that you will enjoy!