Kristiansten Fortress (old spelling Christiansten Fortress, Kristiansten Festning in Norwegian) is located on a hill east of Trondheim, Norway to protect the city against attack from the east. It was built after the city fire of Trondheim in 1681. Constructed finished in 1685. It fulfilled its purpose in 1718 when Swedish forces lay siege of Trondheim. The fortress was decommissioned in 1816 by king Charles John.