Kuressaare

Kuressaare grew beside the bishops' castle on the southern coast of Saaremaa, the island known to German speakers as Ösel. The stone fortress became a principal residence of the bishops of Ösel–Wiek in the late fourteenth century. A small settlement of craftsmen and merchants formed outside its walls, and in 1563 received town rights based on those of Riga.

In 1559 the last bishop sold the castle to Denmark. Danish rulers made it a garrison and strengthened its medieval walls with earthworks, bastions and a moat. The Peace of Brömsebro transferred Saaremaa to Sweden in 1645. Swedish engineers later planned further defences under Erik Dahlberg, adapting the old episcopal residence to the demands of artillery warfare. Kuressaare thus passed from a bishop's seat to a fortified post of rival Baltic monarchies.