Château de Mauvezin, occupied since protohistory, was transformed into a castrum in the Middle Ages and later into a castle. The castle was built by Gaston Fébus (also Phoebus) around 1380. Following the merging of Bigorre into the Kingdom of France in 1607, it fell into disuse and was dismantled piece by piece, its stones being used for other buildings.
Today the castle is being restored and houses a historical and folk museum of Bearn and Bigorre.
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.