 The first mention of Tønder might have been in the mid-12th century, when the Arab geographer Muhammad al-Idrisi mentioned the landmark "Tu(r)ndira", which might have been a reference to either Tønder, or the nearby town of Møgeltønder.Tønder was granted port privileges by the Hanseatic League in 1243, making it Denmark's oldest privileged market town.In 1532 it was hit by severe floods, with water levels reaching 1.8 m in St Laurent's church, 5.3 m above sea level.