A former Viking site on the island of Gotland, Visby was the main centre of the Hanseatic League in the Baltic from the 12th to the 14th century. Its 13th-century ramparts and more than 200 warehouses and wealthy merchants' dwellings from the same period make it the best-preserved fortified commercial city in northern Europe. It is arguably the best-preserved medieval town in Scandinavia and has been named a UNESCO World Heritage Site.