I want to add some day trips including nature into my itinerary and I wanted reviews of the options I am considering. I put the city I would be leaving from for each day trip in brackets. My vacation will be in May, if that's important information. I would prefer options where I can use public transportation instead of renting a car.
Wachau Valley River Cruise (Vienna)
Berchtesgaden Area (Salzburg)
Hallstatt & Dachstein (Salzburg)
Bohemian Switzerland Area (Prague or Dresden)
Feel free to suggest any other nature focused day trips from the cities I listed if you have any favourites!