Founded in the Middle Ages, Rauma grew up on the Bay of Bothnia, where a number of trade routes meet. It was granted its charter in 1442. In 1550, King Gustav Vasa decreed that citizens should be resettled in the new city of Helsinki. The town nonetheless expanded, because its inhabitants returned. It is now a major maritime port and industrial centre. The town is also renowned for its bobbin lace, which has a festival devoted to it in summer, and its regional dialect that is incomprehensible to outsiders.