Sketrick Castle castle dates from the late 12th century. In the 14th century it was acquired by Sir Robert Savage. The Annals of the Four Masters record the capture of the castle in 1470 by an army led by the O'Neill to assist the MacQuillans. They took the castle and it was given to MacQuillan for safe keeping. It was intact until 1896 when a storm demolished much of it.
Sketrick Castle was four storeys high, with a boat bay and a stone subterranean passage discovered in 1957. It had four chambers at ground level, the largest with a vault constructed on wicker centring, as well as two brick-lined recesses, probably ovens. It has lintels running under the bawn wall to a chamber with a corbel over a fresh water spring. Parts of the bawn wall still survive to the north and east of the castle.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.