From Vienna Intl. Airport:
The new City Airport Train, CAT, will take you to the city centre, Station Wien-Mitte in about 16 minutes. Departures every 30 minutes. Underground U4 direction Heiligenstadt to station Friedensbrücke, where you may walk or use Tram No 5 for one stop to the Hotel Bellevue.
From Bratislava Airport:
Together with its partner Slovak Lines, the Postbus offers attractive connections 17 times a day from Vienna Südtiroler via the Vienna Airport to the Slovakian capital Bratislava.
Prices and further information - download PDF-file
Vienna Airport Service:
The Vienna AirportLine connects the most important places in Vienna with the Airport.
Welcome on Board of the Vienna AirportLines!
The Schnellbahn S7 (train) will take you to Wien Mitte in 40 minutes. Further on by Metro U4 direction Heiligenstadt and get of at the station Friedensbrücke. From there you can walk a few minutes or drive one station with the tram nr. 5 until Julius-Tandler-Platz.
From West Railway Station: (Westbahnhof)
Tram 5 direction Praterstern, without having to change until the Franz-Josefs-Bahnhof opposite the Hotel Bellevue.
From South Railway Station: (Südbahnhof)
Tram D direction Nussdorf, without having to change until the Franz-Josefs-Bahnhof opposite the Hotel Bellevue.