My staying in Christian's apartment Sissi was simply perfect. Altought it's not directly in Viena's old town, it's not far and very well located and connected by public transport, with a tram stop almost at the door of the building (1 minute on foot) and different metro stations (Westbahnhof, Längenfeldgasse and Gumpendorfer Straße) just about 7-10 minutes walking distance.
In the surroundings there are supermarkets, bars, restaurants, pharmacies and other shops.
Instead of having keys, you get in the building and the apartment using a code. It was the first time I I used this system and I must say I think it's perfect, very comfortable. You don't have to worry about taking your keys or forgetting them.
When I got in the apartment I was like... WOW! The pictures you can see on the profile are quite good but I think when you see the apartment with your own eyes, it's even bigger than what you see on the pictures. At least this is what I felt. It is quite modern, it has a simple but nice decoration and it is also very well equipped: washing machine, dishwasher, microwave, a big flat screen TV, etc, etc, etc
It has 2 windows, one of them (the right one) has even a nice view of the city. If you want to sleep until late without daylight, simply use the roller blinds fixed to the windows. It's like the night never ends! And even better: the bed is very comfortable! Maybe the pillow could be a little bit better, but it was ok anyway.
I don't know what else I can say about the apartment. If you are looking for a nice apartment in Vienna and you got to this one, book now! I'm completely sure you won't regret!