From the airport
City Airport Train (CAT): Take the CAT until you reach Landstraße/Wien Mitte, which departs every 30 minutes, then transfer to the S-Bahn. After one stop, get off at Rennweg. It's around 20 - 30 minutes trip.
You can choose between a single ticket (2,80€), a day ticket (7,60€) or a ticket for a week (16,20€). Within the ticket price, you can take the train and the bus in the inner circle of vienna.
S-Bahn: Take the S-Bahn (S7) until you reach Rennweg.
Taxi: It is a 15 minutes trip, depending on traffic and cost around 30€.