The apartment is located in an amazing building (it looks like an ambacy). The elevator is very impressive. The apartment is not big, but has everything you need for a quick trip in Vienna (we stayed 3 days). It was spotless clean and all details were considered with the idea to make the place comfortable for visitors like us. There was nothing missing or no issues that bothered us. The host even accommodated our request for an early check in (09:00) and late check out (17:00). He was really hospitable and nice and gave us a few tips for the main attractions and how to reach them. There is a metro station nearby, but we walked most of the time as almost 90% of the sights are within 20 minutes slow walking.
Just a tip from ourselves - look for the cafe called "Edison". It is located just 3-5 minutes away and offers great breakfst at really reasonable prices.