The castle was established in the thirteenth century and became one of the kingdom's strongest castles.
The deposed King Christian II was a captive here from 1532-49 and in 1549-71 King Christian III and Queen Dorothea transformed the castle into a fourwinged Renaissance structure. Later, the castle became the residence of the Dukes of Sønderborg, but between 1718 and 1726 the castle was simplified in the Baroque style due to disrepair. In the nineteenth century the castle served as both Danish and German barracks. In 1921, the structure was bought by the government and thoroughly restored from 1964-73.
The castle chapel is one of Europe's best preserved Renaissance chapels with an original baptismal font, alter piece, and organ.
Most of the rooms in the castle – such as the Great Hall and the residence chambers – are extraordinary in and of themselves.
The museum is centred on the history of the Danish-German border area and illustrates topics such as national identity, national symbols, cultural heritage, customs, and folklore.
Extensive exhibitions about the history of Southern Jutland cover areas from Christian II through the Dukes of Slesvig-Holstein, the wars with Slesvig in 1848-50 and 1864, World War I, the referendum and reunion of 1920, the history of the castle, and the town and the