When I went to Vienna, we stayed at the Hotel Sacher. It's beautiful-they have another in Salzburg. Great location, very comfortable rooms, great service. It's expensive but we were on a tour also and worked through our tour company for a post-tour stay-they have a preferred rate for them so it was discounted.
Try the Le Meridien Vienna. We stayed there three years ago.
The hotel is located at the Ringstraße Boulevard opposite the State Opera and the Kärntner Straße shopping street. The Hofburg Imperial Palace,St. Stephen’s Cathedral and the Karlsplatz underground station are only a few steps away from the hotel.
There is a nice Spa at the Meridien that include a hot tub, a steam bath, a sauna, and a fitness centre and massages are also available. The restaurant Shambala serves creative international cuisine and fine wines. It has a terrace facing the Schillerpark, where snacks, juices and cocktails are served during summer months.
Enjoy strolling in the pedestrian areas around the St. Stephen's Cathedral and pop into one of the many coffee houses. You must try the Sacher Torte mit Schlagober (chocolate cake with whipped cream).