Rosenborg Castle is a Renaissance palace built by King Christian IV in the early 17th century, sitting in the middle of the King's Garden (Kongens Have) just north of the city centre. Christian IV used it as his summer residence and filled it with his personal collections; after his death the castle became a repository for the Danish crown's most prized possessions, and it still is.
The interior, spread across three floors, contains the accumulated treasures of the Danish monarchy: furniture, tapestries, silver, ivory, glass, and the remarkable collection of Dutch flower paintings that Christian IV commissioned. The basement treasury holds the crown jewels — the coronation crown of the absolute monarchs from 1671, the queen's crown, and the regalia used for coronations up to 1840. Rosenborg is one of the most complete and best-preserved royal interiors in Europe.