The medieval layouts of both town centres have remained largely unchanged and illustrate how maritime trading towns were set up under Lübeck law. The architectural heritage, consisting of many outstanding individual buildings, documents the political importance and extraordinary wealth of these Baltic trading ports in the Middle Ages. Wismar is the only Hanseatic town of this size on the southern Baltic to have been preserved virtually intact. Stralsund’s unique island location, between the Strela Sound and a number of lakes dammed up in the 13th century, emphasises the medieval character of its town centre. The ensemble of six monumental brick-built churches provides a remarkable cross-section of the famous ecclesiastical architecture of both Hanseatic towns.