St. John's Church was built in the 13th century, probably between 1234-1297. It was originally home of the Dominican monks, but over the centuries fell into the possession of the Lutherans. It has also served as an arsenal for the city.
The most notable features of this unheralded church are the impressive 15th century sculptures of St. Peter and St. Paul which adorn the the 18th century altar. According the legend two monks who were bricked to the southern wall during the construction. They spent all their life long and were fed trough a window from the outside.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.