We have never been to Vienna and will have 1 and 1/2 days there. Any suggestions on what to see? There will be 3 generations in our group ranging from 9 to 65. We were thinking about the Prater one evening. Is it worth doing a walking tour of the city? I think our hotel is centrally located (it is across from the opera house). Thank you for any suggestions!
Alex, you will find that your location near the opera house is convenient to many Vienna sights, restaurants, and public transit. I recommend that you follow Rick Steves self-guided city walk. You can also tour St. Stephen's Cathedral and the Imperial Apartments at Hofburg Palace. Be sure to allow time to enjoy the food, especially those Viennese pastries. I didn't visit Prater so I don't know if it's worthwhile or not.
Get standing room tickets at the opera. Best value in Vienna, a city with otherwise very expensive sights.
If you are into impressive architecture, you can see much of it by walking. Starting at Stephansplatz you can check out the nearby St Peter's church, Spanish Riding School and Hofburg. You can cross the Volksgarten to the city hall, Parliament then to Theresienplatz and back to the opera. A lot of monumental buildings in a fairly short walk.
The Prater is an amusement park, like you would find at County fair. While it may be fun for the kids, its not in the best area and can be sketchy. They do have a very large ferris wheel that would be the only good attraction for all ages. Try watching the Lipizzaner Stallions practice one morning at the Spanish riding school. Schönbrunn Palace is great and they have a zoo somewhere in the gardens.