The apartment is perfect for two people, perfectly located near the sumptuous Schönbrun palace (20 minutes walking and 10minutes by bus). Very close to the metro station (Johanstrasse exit) that leads to Vienna Center which is the heart of this beautiful city.
Rupert advised us to buy a ticket for a week (18€) and it was a very good idea (economic and practical and includes metro, tram and bus).
Unfortunately, we didn't meet Rupert in Vienna because he was at mission outside the country but his friend has kindly waited for us when our plane was delayed and after being lost before finding the exact adress.
We'll definitely take this flat next time we go back to Vienna.