Vienna, Austria.
Why? Because it's rather cheap (in comparison to other european capitals), according to expats it's the city with the greatest quality of life worldwide and it would be easy to get a dev job, if you need one.
I love Vienna. Would the language barrier be a problem for a non-German speaker? I have no hesitation to learn a different language, though I'd be starting from scratch. How would you compare Vienna to someplace like Berlin?
You don't need to learn German necessarily, I know quite a lot of people there that don't speak German. I was never in Berlin, but my guess is that it is better for developers (Vienna has no startup culture) but at the cost of quality of life.