Vienna is worth spending a day or two in (and I generally really dislike big city tourism)..
Schonbrunn Palace is very nice, and there is some really cool history surrounding its design, the gold eagles at the gates, etc..
St Stephens Cathedral is really neat to check out as well.. there is still a turkish cannon ball embedded in one of the walls from the Ottoman seige of Vienna in the 1600's.. theres a place (I cant remember the name) on a hill a few miles from the Cathedral that overlooks the city that Napoleon sat on to finalize his plan for seizing and occupying the city that provides a beautiful view..
Catch some of the classical music historical venues.. Im not much for classical.. but Schubert, Strauss, and others were born there. Mozart lived there the latter part of his life.. Beethoven lived there for a long time.. etc.. theres some very cool stuff surrounding music in Vienna..
There are quaint coffee houses and restaurants everywhere in the old city..
Austria is on the short list of places I want to take my wife. I've been there a number of times and lived there for about a month years ago while doing some training with Austrian CT units, but she's never been. My plan is to take her to Vienna for a couple of days, Innsbruck for a couple of days, and Hallstatt for a couple of days which is a cool little lakeside village that's absolutely beautiful and has awesome historical aspects. In between planning all of this I somehow ended up going down a rabbit hole researching
แทงบอลโลก which has nothing to do with Austria but the internet is a wild place. Then maybe finish it off with a 2-3 day traditional Austrian hunt for mouflon or red stag.
If you dont have time to get to Vienna, both of the locations you are planning to be in are reasonably close to Salsburg.. I only visited Salsburg once, and only for a single day.. but its a beautiful city, and I would imagine there is a ton to do there as well..