Llansteffan Castle sits on a much older Iron Age promontory fort, proving Llansteffan has been inhabited for several millennia. The hill where the castle stands commands the River Tywi estuary. The hill would have been stripped of trees so that foot soldiers were vulnerable to attack by archers. The original earthworks can still be seen and were used as part of the modern castle's defence system - the castle proper rests within the earthwork rings.
The castle was built by the Normans after 1100 as part of their invasion of Wales and granted to the Marmion family before passing to the de Camvilles through marriage.
It was captured by Maredudd ap Gruffydd in 1146 against the forces of Maurice FitzGerald, Lord of Lanstephan and his brother William FitzGerald, Lord of Emlyn who were the leading Norman settlers of the region. The castle was retaken by the Normans in 1158. Llywelyn the Great recaptured the castle for the Welsh in 1215 and taken back by the de Camville family sometime after 1223. The castle fell to Llywelyn ap Gruffudd in 1257 but returned to the de Camvilles by the 1260s.
The castle was captured twice by the forces of Owain Glyndŵr in 1403 and c.1405. It was recaptured by Sir John Pennes in 1408. The castle was later granted to the Crown and the two-tower Gatehouse was converted into a residence.
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.