Stockholm County Council). Additionally, there are many for-profit private companies offering tours and regular service in the archipelago. City bikes Between April and October, during the warmer months, it is possible to rent Stockholm City Bikes by purchasing a bike card online or through retailers. Cards allow users to rent bikes from any Stockholm City Bikes stand spread across the city and return them in any stand. There are two types of cards: the Season Card (valid from 1 April to 31 October) and the 3-day card. When their validity runs out they can be reactivated and are therefore reusable. Bikes can be used for up to three hours per loan and can be rented from Monday to Sunday from 6 am to 10 pm. Airports International and domestic: Stockholm Arlanda Airport is the largest and busiest airport in Sweden with 27 million passengers in 2017. It is located about north of Stockholm and serves as a hub for Scandinavian Airlines. Stockholm Bromma Airport is located about west of Stockholm. Only international: Stockholm Skavsta Airport is located south of Stockholm. It is located away from Södermanland County capital Nyköping. Stockholm Västerås Airport is located west of Stockholm, in the city of Västerås. The Arlanda Express airport rail link runs between Arlanda Airport and Stockholm Central Station. With a journey of 20 minutes, the train ride is the fastest way of travelling to the city centre. Arlanda Central Station is also served by commuter, regional and intercity trains. Additionally, there are also bus lines, Flygbussarna, that run between central Stockholm and all the airports. there are no airports specifically for general aviation in the Stockholm area. Inter-city trains Stockholm Central Station has train connections to many Swedish cities as well as to Oslo, Norway and Copenhagen, Denmark. The popular X 2000 service to Gothenburg takes three hours. Most of the trains are run by SJ AB. International rankings Stockholm often performs well in international rankings, some of which are mentioned below: In the book The Ultimate Guide to International Marathons (1997), written by Dennis Craythorn and Rich Hanna, Stockholm Marathon is ranked as the best marathon in the world. In the 2006 European Innovation Scoreboard, prepared by the Maastricht Economic Research Institute on Innovation and Technology (MERIT) and the Joint Research Centre's Institute for the Protection and the Security of the Citizen of the European Commission, Stockholm was ranked as the