Billnäs ironworks was founded in 1641 by Carl Billsten. It faced many difficulties during 17th and 18th century. Local peasants destroyed the ironworks already in 1659 because of too heavy taxation. During the Great Wrath Russians occupied and destroyed it again in the 18th century.
Billnäs Ironworks moved to Hisinger family's possession in 1723. Bar hammer workshops with forges and waterwheels, and coal rooms were built to both sides of the rapids in Billnäs Ironworks. Johan Hisinger was especially active in building and developing the Ironworks’ operations. Billnäs manufactured many kind of forge products until 1920, when it was incorporated into Fiskars Corporation (the another ironworks site nearby).
An industrial business ended in Billnäs in the end of the 20th century. Today it’s moved to the use of service industry. Various public events, concerts and exhibitions among others, are organized in the Billnäs Ironworks. In the long run, hotel- and restaurant operations are planned to the area as well as a full renovation of the valuable real estates. The ironworks area is today a well-preserved national heritage. The most valuable building is the great forge from the 17th 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.