The ways to reach the Apartments Mühlgasse:

Take the City Airport Train (CAT) to Wien Mitte
Then withe the Underground (U4 in direction Hütteldorf) to Kettenbrückengasse. From there walk along Naschmarkt, right to  Schikanedergasse and left to Mühlgasse.

www.cityairporttrain.at

By car:

From west (Westautobahn A1):
exit Zentrum > Schönbrunner Straße > Rechte Wienzeile
> Schikanedergasse > Mühlgasse.
 
From south (Südautobahn A2): exit Zentrum,> Triester Straße > Matzleinsdorfer Platz. > Reinprechtsdorfer Straße > Schönbrunner Straße > Rechte Wienzeile > Schikanedergasse, left to Mühlgasse.

Routenplaner (Google-Maps)