I cannot imagine beating Gerta's apartment for convenience. If a place of interest is not within a walking distance (most tourist attractions are), then Wien Mitte/Landstrasse station offers connections to all of Vienna including the airport (line S7 is pretty much as convenient as CAT train from the airport, runs from the same platforms with the same frequency as CAT and is considerably cheaper). Considering the location in such a busy city hub, the apartment is relatively quiet. Gerta is warm and welcoming, clearly taking pride in her place and maintaining it very well. The apartment is bright and cheerful. I feel lucky to have chosen this host and this place.