Rostock is a city in the German state of Mecklenburg-Vorpommern, in north-eastern Germany. The city is close to the mouth of river Warnow by the Baltic Sea, and is the third largest Baltic Sea port in Germany, with ferry traffic to Trelleborg in Sweden, for example. During the Middle Ages Rostock was an important city in the Hanseatic League. During World War II many historical buildings and memorials were destroyed. The city has a university and also a college of music and theatre. Rostock is big in water sports, primarily sailing.