At the time when southern Sweden was in the hands of the Danes this castle was nicknamed "the key to Sweden" due to its strategic position. The initial keep (12C) belonged to a defensive line reaching from Öland island to the coast. King Gustav Vasa reinforced fortifications in the 16C and rebuilt the castle. His sons transformed the interior to suit the Renaissance style. The splendid ceremonial apartments reflect the pomp and glamour of this period. Another must-see: King Erik's sumptuous bedroom.