The island of Sylt was a famous destination for leisure and holidays in the early 20th century. Sylt's first small airport was established right after World War I, and in 1919 the first scheduled routes to Weimar, Hamburg and Berlin commenced. As Germany had lost the mainland port serving Sylt due to the Treaty of Versailles, the airport became an important way for travelers to avoid entering Denmark, before the construction of the "Hindenburg causeway" linking Sylt to the mainland by railway.