Founded in 1308 to defend this marshy region, the fortress played a decisive role in the Nordic Seven Years War (1563-1570). King Chrisian IV of Denmark added star-shaped bastions around the castle, which was converted into a Renaissance palace. After the Treaty of Roskilde (1658), the fortress became Swedish. Thus no longer of strategic importance, it fell to ruin. The imposing round tower nicknamed Fars Hatt (Father's Hat) is the only corner tower still standing. In summer, concerts and other events are held in the inner courtyard.