Raised by Haakon V of Norway at the end of the 13th century, this fortress on a headland by the fjord has withstood every siege it has faced.
Nearly all of these were conducted by Swedish forces, whether it was Duke Eric of Södermanland at the beginning of the 14th century or King Charles XII in 1716.
The surviving design is from the reign of King Christian IV, who moved the whole of Oslo just to the north of the fortress after a fire in 1624. He modernised the defences and built a palace in the Italian Renaissance style at its heart.
