Hünenberg Castle was built in the 12th century and mentioned first time in 1173. At the Battle of Sempach in 1386 Hünenberg fought on the side of Habsburg family and the castle was destroyed after the defeat. During the following three decades the Hünenberg family also lost their power and reputation. In 1416, Rudolf von Hünenberg sold the ruined castle and its rights to the Bütler brothers. The keep was still standing into the 19th century.
Kristiansten Fortress was built to protect the city against attack from the east. Construction was finished in 1685. General Johan Caspar von Cicignon, who was chief inspector of kuks fortifications, was responsible for the new town plan of Trondheim after the great fire of 18 April 1681. He also made the plans for the construction of Kristiansten Fortress.
The fortress was built during the period from 1682 to 1684 and strengthened to a complete defence fortification in 1691 by building an advanced post Kristiandsands bastion in the east and in 1695 with the now vanished Møllenberg skanse by the river Nidelven. These fortifications were encircled by a continuous palisade and thereby connected to the fortified city. In 1750 the fortress was modernized with new bastions and casemates to protect against mortar artillery.