Month in Europe, seeking advice on must do’s and can skips.

We are looking at our first trip. Wanting a vacation. Meaning not every day to be a race to see ever cathedral, landmark, castle, etc.

We are kind of thinking an air b and b in Italian country side. Then train to other areas with a general idea to end up in normandy before coming home. We’re not opposed to UK, but not a “Must”. Kind of looking for some ideas. Nothing is really a must, but some things we’d like to see are the vatican, and some WWII sites. We’d love to hit Austria if possible to fit in.

Completely new to all this, so any advise would be appreciated. We are rural US folks, so we appreciate small communities. We don’t mind visiting cities, but spending all our time in Rome, Paris, London, etc doesn’t really strike us as a vacation either.