Personally, I'd vote Germany. If nothing else, the language is relatively easy to learn all told. After a lifetime of speaking english, the fact that there exists a language with relatively solid rules of syntax and grammar is refreshing. And once I found that the extremely long words German is so fond of is often really just a collection of smaller words for the most part, most of the intimidation factor went away.
Beyond that, it's location gives ready access via rail to a number of places you might also want to go and also sports some of the most fascinating history in Europe.
Beyond that, it's location gives ready access via rail to a number of places you might also want to go and also sports some of the most fascinating history in Europe.