Hagby Church is one of Sweden's few preserved round churches, and is considered by many to be the best preserved one in the country. The predecessor of Hagby stone church was the wooded Saint Sigfrid chapel, which was located about two kilometres south of the present church structure. The construction of this stone church began in the late 12th century. By 1541 it was abandoned.
The structure was meant to serve both as a sanctuary and a fortified building. As a result, the upper part of the walls has openings for shooting and spear throwing. The most recent renovation has attempted to emphasize the old nature of the building, so that it is now perhaps the best example of round church architecture, which otherwise is generally mostly found on the island of Bornholm. The triumph crucifix and font dates from the Middle Ages, but the interior is mainly from the 17th and 18th centuries.
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.