If you travel by air, it is recommended to fly into Cologne/Bonn, Frankfurt or Düsseldorf. In all cases, you continue your travel by train. The lowest average travel time would be from Cologne/Bonn (about 1h 40 min). From Frankfurt, it takes between 2h and 2h 30 min. Travelling from Dusseldorf to Siegen takes about 2h 30min. If you plan to take a train from any of these stations go to http://www.bahn.de/international/view/en/index.shtml where you can search for the best connection. Please put “Köln/Bonn Flughafen”, “Frankfurt (M) Flughafen”, “Düsseldorf Flughafen”, “Dortmund Flughafen” as your departure station and “Siegen“ as your destination.