We had a realy great stay in Johannes and Veronika's flat.
It's realy well located, in center Vienna : we could walk to visit a lot of museums or easily have a tram.
The building is very beautiful and the flat is furnished in a way you feel like leaving at Stefan Zweig time, while you find modern comfort.
Johannes answered very quickly when we had questions or requests. Everything was done so that we spend a great stay !