We had such a great time at Ralf's apartment. It is in a very peaceful location with so much to do all around it. And Belvedere Palace is only a 10-15 minute walk away! There is public transportation right around the corner but we didn't even end up using it. We walked everywhere. Including Stephansdom which was only a 20 minute walk. Ralf was very helpful the entire stay and even helped us find our way to the apartment, where his very nice house keeper greeted us. The only minor thing is, I think the washer might be broken? It washed our clothes but was SO loud that I thought it was going to blow up. It even bounced forward a few inches. This obviously isn't a big deal, just be warned and definitely don't do laundry at night!
Anyway, I highly recommend this apartment to anyone visiting Vienna and would definitely stay there again myself!
Thanks for the hospitality Ralf! And the champagne and breakfast food!