Jacob had close connections with King Eric II of Norway and as a result got substantial Norwegian assistance with the construction.
Their sonMagnus Eriksson, King of Sweden and Norway, spent much time at the fortress as well.
[2] The fortress was augmented during the late 16th and early 17th century on order by King Christian IV of Denmark.
It is currently used as a museum and has a couple of notable pieces on permanent exhibit: Bocksten Man with the only complete clothing from the 1300s known to have been worn by a single individual, and the button that supposedly killed Charles XII of Sweden.
In August 2006, a couple of witnesses claimed to have seen the monster emerge from the dark water and devour a duck.