Hi
I've visited Vienna recently and did so many years ago.
Top attractions include:
St Stephan's Dom (Cathederal)
Schloss Schonbrunn
Schloss Schoenbrunn
Kunsthistorisches Museum - various locations but amazing art
KHM
Opera and music in general are important
The Prater (public amusement park)
Architecture tends towards the Baroque and can be fascinatingly kitsch.
Wine tasting places
Heuriger
Outside Vienna, I recommend the monastry at Melk.
That should be a good start...just use that as a basis for web searches.
KP