Caerphilly Castle is a medieval fortification constructed by Gilbert de Clare in the 13th century. Surrounded by extensive artificial lakes – considered by historian Allen Brown to be 'the most elaborate water defences in all Britain' – it occupies around 30 acres and is the largest castle in Wales and the second-largest castle in the United Kingdom after Windsor Castle. It is famous for having introduced concentric castle defences to Britain and for its large gatehouses.
Gilbert began work on the castle in 1268 following his occupation of the north of Glamorgan, with the majority of the construction occurring over the next three years at a considerable cost. The project was opposed by Gilbert's Welsh rival Llywelyn ap Gruffudd, leading to the site being burnt in 1270 and taken over by royal officials in 1271. Despite these interruptions, Gilbert successfully completed the castle and took control of the region. The core of Caerphilly Castle, including the castle's luxurious accommodation, was built on what became a central island, surrounding by several artificial lakes, a design Gilbert probably derived from that at Kenilworth. The dams for these lakes were further fortified, and an island to the west provided additional protection. The concentric rings of walls inspired Edward I's castles.
The castle was attacked during the Madog ap Llywelyn revolt of 1294, the Llywelyn Bren uprising in 1316 and during the overthrow of Edward II in 1326–27. In the late 15th century, however, it fell into decline and by the 16th century the lakes had drained away and the walls were robbed of their stone. The Marquesses of Bute acquired the property in 1776 and under the third and fourth Marquesses extensive restoration took place. In 1950 the castle and grounds were given to the state and the water defences were re-flooded. In the 21st century, the Welsh heritage agency Cadw manages the site as a tourist attraction.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.