Basmo fortress is located in the north-western part of Marker municipality in Østfold near the Swedish border on an isolated mountain outcropping between Rødenessjøen and Hemnessjøen. It was constructed in the 1680s and was abandoned after 62 years of service in 1745. The first mention of this Norwegian fortress is in a letter from Field Marshal Wedel Jarlsberg to the King in 1683. Major General Johan Caspar von Cicignon developed the plans. During the Great Northern War it was manned by up to 1,350 men.