[1] The castle was built in 1175 by King Valdemar I of Denmark as a defensive fortress, and as a base from which to launch raids against the German coast.
King Valdemar II similarly used the castle for expansion into the Baltic, and in 1241, it was where he created the reformed legal system, the Code of Jutland.
Large parts of the castle were demolished after the Swedish wars had ended, in order to construct a palace for Prince George, son of King Frederick III.
Three manors were constructed nearby, including Iselingen, which became a meeting place for many leading artists and scientists during the 19th century.
The only fully preserved part of the castle, the 26 meter tall Goose Tower (Gåsetårnet), is the symbol of the city.