It all depends on what you like of course. A few places in Austria that I've enjoyed visiting are
Hallstadt, near Salzburg - Austria's oldest recorded settlement. The nearby saltmine is quite interesting too.
There are some ice caves in the Dacshstein - near Obertraun:
Hohenwerfen castle just north of Bischofshofen (if you go a the right times they have a bird of prey display) - used for many of the shots in Where Eagles Dare.
- similarly Hochosterwitz castle down south near St.Veith north of Klagenfurt is pretty impresive.
Another castle - this time more of a ruin - is D?rnstein on the Danube - where Richard the Lionheart was held captive on his return from the crusades. This is also in the heart of the "Wachau", one of Austria's best wine regions (no antifreeze here)
There are a number of busy beaches on the lakes between Klagenfurt and Villach. They regularly have large Harley/Bike/Golf GTI type rallies around that area as well.
If you go over to Slovenia/Croatia, I enjoyed Piran, on the Istrian coast. Lubljana is a busy university town with all the night-life to go with it . Also a nice old town centre.
Further south on the island of Krk (reached by an impressive bridge) is the towm of Krk itself - with a good beache to the east of it at Baska.
There is the Plitvicka National Park in Croatia which has some stunning lakes, caves and waterfalls.
If you go that way and ride through the mountains there you'll almost certainly be struck by the sight of the war-scarred houses if you get even a little off the beaten track.
The Dalmatian coastal road, despite being very
curvy is only fun if you're not in a hurry. It's busy and remarkably dangerous. The scenery is brilliant, though.
Maybe some of these things'll grab you.