I can recommend staying in Katalina's small guest house or however you want to call it. The check-in was well described but rather complicated considering that you have to download an app to for unlocking the locks to the guest house and your booked apartment. The location of the apartments is great though. The apartment is clean and cosy. The apartment I stayed in had some problems with the light and the light switchs (they had to be pressed really hard in order to work). Other than that everything worked well. I can recommend Katalina's guest house for a low profile stay in Vienna.