The wooden Kastellet fortress on the island of Kastellholmen was built as a defensive structure in 1667. Before that, there were only a small guardhouse and a flagpole on the site of the future fortification.
After some time, Kastellet lost its original function, as the Swedish navy moved to another location, and later it became a cultural symbol altogether.
The wooden structure was replaced with a stone one in the middle of the 18th century, and in the 19th century a gunpowder production laboratory was set up in Kastellet Castle. In 1845, a major explosion occurred there; there were no casualties, but a significant reconstruction took place in 1846-1848. It was led by the architect Fredrik Blom.
Today, Kastellet Castle is a round tower with red brick walls and a 20-meter-high flight of stairs. Every morning, the Swedish naval flag is raised over the former fortress, symbolizing peace and the fact that the country is not occupied by enemy troops and is not involved in military operations.
