Regional train from Vienna to Bratislava

Regional trains leave from Wien Hauptbahnhof, which is not on the closed section of the S-Bahn. Some go via Marchegg to Bratislava hlavná stanica, the main station, about 15–20 minutes' walk from the old town; others, via Kittsee to Bratislava-Petržalka, on the other side of the Danube. The two stations are not interchangeable: check which one your ticket says. Check the timetable on ÖBB before you set off.