Christiana's apartment is wonderful - I would recommend staying there to any of my friends or family visiting Vienna. It is just as you see in the photos, spacious and artistic. There is plenty of natural light and it is very clean. The bathrooms and showers were fantastic! As were the blackout blinds. We didn't get around to using the sauna, but it would probably be amazing in winter!
The apartment is located in a really cool part of town that is well worth exploring and is only a short walk to the city centre via some of the main sights. If you're not keen on walking, the subway is about 2-5mins. There are some great coffee shops and bakeries nearby where we got our breakfast daily.
Christiana was able to accommodate us with an early check-in. She came to meet us and settle us in, and also provided us with a lot of information about how we could maximise our time in Vienna.
I would absolutely recommend a stay at Christiana's apartment.