The Kalmar Strait (Swedish: Kalmarsund) is a strait in the Baltic Sea, located between the Swedish island of Öland and the province of Småland of the Swedish mainland. The strait is about 130 kilometres (81 mi) long and between 5 kilometres (3.1 mi) and 25 kilometres (16 mi) in width. There is a road bridge across the strait, the Öland Bridge, opened in September 1972. Prehistory. The areas along the Kalmar Strait have a heritage of Neolithic and Bronze Age habitation.
https://en.wikipedia.org/wiki/Kalmar_Strait