I plan to spend 5 days in Austria, my major city is Vienna. I am thing to do a day trip to Salzburg from Vienna. But after researching a little bit, there are actually lots of things to do, I wonder if a day will be enough or if I should do more days. I hate keep moving the luggage around for just 1 or 2 days trip though. And I definitely don't want to spend my 5 days in Vienna, I am afraid running out the things to do. What's your recommendation?