Oresund

The Sound (locally known as Sundet, Danish, Øresund or Swedish Öresund,  is the strait that separates the Danish island Zealand from the southern Swedish Province of Scania. Its width is just 4 kilometres (2.5 mi) at the narrowest point between Helsingor, Denmark, and Helsingborg, Sweden.

Political control of Øresund has been an important issue in Danish and Swedish  history. Denmark maintained military control with the coastal fortress if Kronborg at Elsinore on the west side and Karnan at Helsingborg on the east, until the eastern shore was ceded to Sweden in 1658. Both fortresses are located where the strait is just 4 kilometers wide.