The Church of Saint-Pierre (Église Saint-Pierre) was built in the early 13th and the construction continued until the 16th century. The spire was destroyed in 1944, and has since been rebuilt. The eastern apse of the church was built by Hector Sohier between 1518 and 1545. The interior choir and the exterior apse display an architecture that embodies the transition from Gothic to Renaissance.
Until around the mid 19th century, the eastern end of the church faced onto a canal that was then covered and replaced by a road. Various artists and engravers recorded this relation of the church to the canal; for instance, the Scottish painter David Roberts made several very similar views, one of which (dated to c.1830) is in Musée des Beaux-Arts in the Château de Caen.
References: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.