It feels very strange to disagree with dear Pilot DAR
but I would rather agree with BackPacker in this case: stay away from the high ground - unless you know what you are doing. Especially because of the increased unreliability of weather. But it must be said that, as a pilot, I don't come even near his level of expertise.
Also it would be good to have a better idea of your flight:
* as already asked: VFR? IFR? Will you consider "VFR on top"?
* how many stops do you plan en route, or in other words, what's your bladder endurance?
* what fuel do you require, Avgas or Mogas?
* what makes an aerodrome "interesting" for you? I agree with the suggestion of hotel and restaurant, but perhaps you'll enjoy a museum visit also?
That said, a few ideas:
* generally, you almost can't go wrong in Germany. Plenty of well-equipped fields, many with a decent or outright good eatery. Fine radio comm's, too, generally.
* France is a bit more varied but still good. And you cannot avoid it anyway. "incontournable" as they say there. Beware of fields that do R/T only in local language.
* Speyer EDRY has a famous museum of aviation and more technology
* the Stampe & Vertongen museum at Antwerp EBAW is nice too, and so is the city, and the airport restaurant. A bit out of your way, though, perhaps
* Bremgarten EDTG must have a collection of warbirds but I never went there.
* Schwäbisch Hall has two aerodromes, EDTX and EDTY, one very rural, the other high-end. Very nice Italian resto on the northern one. The city has a reputation for beauty, too, with many historical buildings.
* I read good reports about Coburg, spectacular approach over the city.
* if mountain flying does not deter you, think of La Cerdanya LECD