Rosenborg was once the favored residence of 17th-century King Christian IV, who crammed it full of delightful trinkets and toys, from priceless art objects to technological inventions of his time. The residence was opened to the public in 1838, and today houses all of the aforementioned objects in addition to the crown jewels and a nice selection of royal weapons. A standout of the collection is the Golden Crown of Absolute Monarchy, a sapphire, diamond, and ruby-encrusted wonder that has been used by the kings and queens of Denmark for 170 years. Admission is 90 DKK.