trains for services to stations in the Stuttgart metropolitan area. The local rail networks (see above) operate underneath the terminus. Stuttgart also has its own rail freight centre with marshalling yards and a container terminal in the Obertürkheim area of Hedelfingen. Rail: The Stuttgart 21 project After years of political debate and controversy, plans were approved in October 2007 to convert the existing above-ground main train station to an underground through station. The Stuttgart 21 project will include the rebuilding of surface and underground lines connecting the station in Stuttgart's enclosed central valley with existing railway and underground lines. Building work started in 2010 with controversial modifications to the Hauptbahnhof and was slated to be completed in 2019, then 2021 and now 2025. Air transport Stuttgart is served by Stuttgart Airport (, IATA airport code STR), an international airport approximately south of the city centre on land belonging mainly to neighboring towns. It takes 30 minutes to reach the airport from the city center using S-Bahn lines S2 or S3 or Stadtbahn line U6. Stuttgart airport is Germany's only international airport with one runway. Despite protests and local initiatives, surveys are currently underway to assess the impact of a second runway. Road transport Stuttgart is served by Autobahn A8, that runs east–west from Karlsruhe to Munich, and Autobahn A81 that runs north–south from Würzburg to Singen. The Autobahn A831 is a short spur entering the southern side of Stuttgart. Besides these Autobahns, Stuttgart is served by a large number of expressways, many of which are built to Autobahn standards, and were once intended to carry an A-number. Important expressways like B10, B14, B27 and B29 connect Stuttgart with its suburbs. Due to the hilly surroundings, there are many road tunnels in and around Stuttgart. There are also a number of road tunnels under intersections in the center of Stuttgart. Waterways Stuttgart has an inland port in Hedelfingen on the Neckar. Sport Football As in many parts of Germany, football is the most popular sport in Stuttgart which is home to 'The Reds' and 'The Blues'. 'The Reds', VfB Stuttgart, are the most famous and popular local club. An established team currently playing in the German Bundesliga, VfB was founded in 1893 and has won five German titles since 1950, most recently in 1992 and 2007. VfB is based at the Mercedes-Benz Arena in Bad Cannstatt. 'The Blues', Stuttgarter Kickers, are