Kronborg was repaired by Christian IV after fire damage in 1629 and sacked and occupied by the Swedes between 1658 and 1660.In the 18th century the Kronborg fortress was extended and the castle restored, serving as a garrison from 1785 to 1924; the palace chapel was restored from 1838 to 1843. Other restorations were carried out from 1866 to 1897 and from 1925 to 1937. In 1915 the Trade and Shipping Museum was installed in the north wing.The plan of Kronborg Castle was determined by its predecessor, which it effectively encapsulated, its outer surround corresponding to the medieval curtain. Frederick II’s rebuilding began with the great cannon tower over the southern part of the palace, while the old royal residence was extended to the west for the castellan’s apartments and the administrative offices. The castle chapel was installed in the south wing.By 1579 a third storey had been added to the south wing to accommodate the great ceremonial hall, and the octagonal stair-tower heightened and equipped with a balcony for trumpeters.