Kristiansten Fortress

Kristiansten Fortress is located on a hill east of the city of Trondheim in Trøndelag county, Norway, named after Christian V of Denmark-Norway. It was built after the city fire of Trondheim in 1681 to protect the city against attack from the east. Construction was finished in 1685. It fulfilled its purpose in 1718 when Swedish forces laid siege against Trondheim. The fortress was decommissioned in 1816 by King Charles XIV John.

Source: Wikipedia