Before it was a palace it was Hillerødsholm — the islet of Hillerød — a half-timbered house on the northernmost of three small islands in a North Zealand lake. It belonged to the Gøye family; Mogens Gøye, Steward of the Realm and one of the architects of the Danish Reformation, lived there. His daughter Birgitte and her husband, the naval commander Herluf Trolle, inherited it and built something grander in the 1540s. In 1550 they swapped it away: Frederik II wanted the estate for its hunting, and traded them the manor of Skovkloster in southern Zealand for it. The king extended the house in 1560, asked Trolle to stay on and supervise the work, and renamed the place after himself. Frederiksborg. Frederik's castle.

Frederik's son Christian was born there and loved the place — which did not stop him from demolishing it. Reigning as Christian IV, he pulled down his father's castle in 1599 and hired the Flemish architect Hans van Steenwinckel the Elder to replace it in the Dutch Renaissance manner. Steenwinckel died in 1601; his sons Hans and Lorenz finished the job. The four-storey main building and its three wings stood by around 1610, the chapel by 1618, the whole complex by roughly 1620 — under a decade of work for the main structure, which was extraordinary for the period. Red brick, stepped gables, sandstone dressings, copper spires, towers at every outer corner, all of it rising straight out of the water.

For two centuries the castle mattered less as a residence than as a stage. Every Danish monarch from 1671 to 1840 except Christian VII was crowned and anointed in its chapel. In 1659, during the Second Northern War, Swedish troops took the castle and carried off most of its art as reparations. Then came Frederik VII's cold December night. The fire tore through the state rooms and gutted them, and three workmen were killed when a vault in the church collapsed. What survived was structural and lucky — the outer walls, the towers, and the chapel, whose heavy vaulting held.

Denmark treated the loss as a national bereavement rather than a royal inconvenience. Money came from public subscriptions, from the crown, from parliamentary grants, and from an arts-and-crafts lottery set up in November 1861. Ferdinand Meldahl began the reconstruction in 1860, working from archived plans and from the meticulous architectural paintings Heinrich Hansen had made of the interiors before they burned; by 1864 the exterior looked as it had. The decisive intervention came from a brewer. J. C. Jacobsen, the founder of Carlsberg, put up 200,000 kroner in 1877 for the King's Wing on one condition: that the castle become a museum of Danish national history. The Carlsberg Foundation added an annual grant and half the yield of a one-million-krone endowment. A royal decree of 5 April 1878 created the museum; it opened on 1 February 1882, and in 1888 the courtyard's Neptune Fountain — the original carried off by the Swedes in 1659 — was recast in bronze at Jacobsen's expense. Scandinavia's grandest Renaissance palace survives because a man who sold lager decided it should.

The chapel, consecrated in 1617, is the best-preserved Renaissance interior in the complex: a long nave under a six-vaulted stucco ceiling, two storeys of galleries on pillars painted with grisaille biblical figures in the 1690s, an altarpiece and pulpit by the Hamburg silversmith Jacob Mores. Its treasure is the Compenius organ, installed by Esaias Compenius himself shortly before he died at Hillerød in 1617. It is the oldest organ in Denmark, it has 1,001 wooden pipes, its original hand-pumped bellows still work, and it is finished in ebony, ivory and silver. Since 1693 it has been the ceremonial church of the Orders of the Elephant and the Dannebrog, and the coats of arms of their recipients line the walls — Niels Bohr, Nelson Mandela. The Audience Chamber survived too: finished for Christian V in 1689 by Lambert van Haven, it is the oldest Baroque room in the country, crowned with triumphant scenes from the Scanian War of 1675-1679, a war Denmark lost.

The paintings rescued on the night of the fire became the seed of a collection that now fills some seventy rooms and holds more portraits than anywhere else in Denmark. The Valdemar Room carries the story from the twelfth century to the seventeenth, with pictures commissioned specially for the museum — Carl Bloch's imprisoned Christian II, Otto Bache's conspirators galloping away from Finderup after the murder of Erik Klipping. A copy of the oldest known Dannebrog, dating from 1427, hangs there; the original was in Lübeck Cathedral until bombing destroyed it in 1942. Since 2010 the museum has also run an annual juried international portrait exhibition — fitting, in a building whose second life began with somebody carrying pictures out of a burning room.