 Nothing at all
 Everything about this hotel was great I checked in via an app on my phone so was able to go straight to my room when I arrived no need for any checkin with staff Some reviews say this hotel is a little out of the centre of the city I disagree The location is fantastic The tram literally collects you at the front door and takes you right into the heart of things in no time and they run pretty much all day and night meaning you have a peaceful nights sleep with no noise from late night bars and restaurants etc I had tickets for the opera and one of the tram stops is right outside the opera house which itself is in the heart of Vienna All in all I couldn t fault this place one bit 