Hay Castle is a medieval fortification and 17th-century mansion house in the small town of Hay-on-Wye, Wales. Originally constructed as part of the Norman invasion of Wales, the castle was designed as a ringwork overlooking the town in either the late-11th or early-12th centuries. It was rebuilt in stone around 1200 by the de Braose family and then had a turbulent history, being attacked and burnt several times during the First and Second Barons' Wars, the wars with the Welsh princes, the rebellion of Owain Glyndŵr and the Wars of the Roses.
In the 17th century a Jacobean mansion house was built alongside the medieval keep and the property became a private home. Serious fires in 1939 and 1977 gutted the castle and, despite repairs in the 1980s, by the 21st century much of the building was derelict and unstable. Since 2011 it has been owned by the Hay Castle Trust who plan to renovate the property to form an arts and education centre.
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.