The majority of international cargo shipments are handled at ports. Vuosaari Harbour in Helsinki is the largest container port in Finland; others include Kotka, Hamina, Hanko, Pori, Rauma, and Oulu. There is passenger traffic from Helsinki and Turku, which have ferry connections to Tallinn, Mariehamn, Stockholm and Travemünde. The Helsinki-Tallinn route – one of the busiest passenger sea routes in the world – has also been served by a helicopter line, and the Helsinki-Tallinn Tunnel has been proposed to provide railway services between the two cities. Largely following the example of the Øresund Bridge between Sweden and Denmark, the Kvarken Bridge connecting Umeå in Sweden and Vaasa in Finland to cross the Gulf of Bothnia has also been planned for decades.