If you had one full day (and one night) in Salzburg, how would you spend it?
I would visit Mirabell Gardens, the fortress, St Peters Cemetery, wander through the squares and lanes of old town, and attend a Mozart concert. In the evening, I would go out again through the squares with fountains that are lit. I would the go towards the river to get a good view of old town lit and the lights on the fortress. There is much more to do, but that would be enough for one day for me.
I would also add a walk to the Augustiner brewery for dinner and a nice cold beer! We were surrounded by locals there and loved it.