Austria-Vienna and also get to Budapest it’s like 2-3 hours and there is a dedicated train.

Hallstatt.

Between Salzburg and Hallstatt is Burg Hohenwerfen which is great.

Lake Bled in Slovenia.

We loved Ljubljana just roaming and taking it in.

There is a HUGE underground cave in Postojnskajama and a neat castle nearby nestled into a recess. Highly recommend the cave.

Plitvicka national park is in northern Croatia and Rovinj is nearby. Not super close but both great.

Driving through the Dolomites of northern Italy phenomenal.

Venice is also possible in that area.