Megalithic burial places and archaeological finds testify that the island of Rügen was already inhabited around 6000 BC. Between the 3rd and 6th centuries the Germanic tribes left the island in the course of the migration of peoples and the Slavs immigrated to Rügen. Around the year 1000 the chronicler Adam von Bremen wrote, for the first time, about the island of Rügen. The Danish King Waldemar I conquered it in 1168 and began to convert the inhabitants to Christianity. Simultaneously the first German colonists were beginning to settle on Rügen. The dukes of Pomerania took over the political power in 1325. The churches, however, belonged to the Danish diocese Roskilde for another two centuries. The Thirty Years? War brought death and destruction to Rügen: Hunger and the plague took the lives of many people. The town suffered looting and pillage by soldiers. In 1648 the Treaty of Westphalia legitimised the occupation of Rügen by the Swedes. It was not until 1815 that the Prussians took power. The 19th century changed the economic structure of the island: in 1806 the Swedish king abolished serfdom. By the end of the century tourism had developed into an important branch of industry. The host of visitors in the newly founded seaside resort made it necessary to develop the lines of communication: train ferries have connected Rügen to the mainland since 1883, since 1909 also with the Swedish Trelleborg. The narrow-gauge railway ?Rasender Roland? ("Scorching Roland") began operating in 1895. National Socialism left less destruction on the island than construction projects. Since 1936 the island has been linked to the mainland via the Rügen dam. The same year the construction of the gigantic Prora Health Resort began. The Colossus of Rügen - "Koloss von Rügen"- was never completed. In 1953 the leaders of the German Democratic Republic also expropriated hotels, guest houses and restaurants. Only after the 1970s was tourism promoted again. Since German Unification great sums of money have been invested in the Baltic seaside resorts. The historical seaside resort architecture and the piers dominate the appearance of most seaside towns.