Köln/Bonn airport (Flughafen; www.koeln-bonn-airport.de) is 17km south of Cologne's centre, and is practically halfway Bonn. It is serviced by S13 S-Bahn trains, departing from the station underneath Terminal 2. Some DB regional and long-distance trains also stop at the airport. The journey to Hauptbahnhof (the main station) takes around 20 minutes and costs €2.30. Tickets can be purchased at vending machines in the station or from the DB service desk inside Terminal 2, and do not require validation. You can also hail a taxi from outside the arrival terminal. The trip into town takes 20-25 minutes and costs around €25. Six car rental companies have offices in hall between terminals 1 and 2.