From Hotel Wandl take the Underground (U1) from Stephansplatz, direction Reumannplatz, and get off at 'Südtiroler Platz'. The big bus terminal is right close to the exit of the Underground. Go to platform no. 22 - 24 and look for the post buses going in the direction 'Eisenstadt', buses no. 566/567/766.

From Hotel Prinz Eugen the bus terminal is located some 100 meters just opposite to the hotel, on your right, close to the exit of the Underground at 'Südtiroler Platz'. Go to platform no. 22 - 24 and look for the post buses going in the direction 'Eisenstadt', buses no. 566/567/766.

You can view the bus schedule at
http://www.iiasa.ac.at/Admin/CVS/docs/transportation.htm

It takes about 30 minutes to get from Vienna 'Südtiroler Platz' to Laxenburg 'Franz Josef Platz'. You can purchase the ticket directly in the bus at Euro 1.50. To take a taxi from the airport direct to IIASA in Laxenburg will cost about Euro 40.00.