We stayed for two nights at Carina & Georg's apartment. It's a single-room apartment with a kitchen and bathroom. The main room is spacious, with high ceilings. Comfortable bed. Everything was clean. Not too hot either (we stayed during some wam days in the summer). There were a bit of noise from the street, but we slept through it and weren't too bothered. Carina & Georg were very communicative, and checking in and out was really quick and easy. Getting to the city centre is easy as well, by foot or by metro. I can easily recommend the apartment to anyone staying in Vienna.