From 990 AD, Château de Castelnou served as the administrative and military capital of the Viscount of Vallespir. Its irregular pentagonal plan follows the rocky outcrop on which it was built, this elevated position providing defence against enemy attacks.
The castle was taken by the troops of James II of Majorca en 1286, and again in 1483. Largely demolished in 1559, it was no longer restored or inhabited and deteriorated throughout the 17th and 18th centuries. At the time of the French Revolution it became the property of the commune. It was sold to Viscount Satgé in 1875 and, by 1900, had become again an elegant and habitable fortress. It was acquired in 1946 by Charles-Emmanuel Brousse who was married to Amy Elizabeth Thorpe, a famed American spy. Having been ravaged by a terrible fire, in 1987 it was sold and has since been restored.References:
Ängsö Castle was first named as "Engsev" in a royal charter by king Canute I of Sweden (r. 1167-1196), in which he stated that he had inherited the property after his father Eric IX of Sweden. Until 1272, it was owned by the Riseberga Abbey, and then taken over by Gregers Birgersson.
From 1475 until 1710, it was owned by the Sparre family. The current castle was built as a fortress by riksråd Bengt Fadersson Sparre in the 1480s. In 1522, Ängsö Castle was taken after a siege by king Gustav Vasa, since its owner, Fadersson's son Knut Bengtsson, sided with Christian II of Denmark. However, in 1538 it was given by the king to Bengtsson's daughter Hillevi Knutsdotter, who was married to Arvid Trolle.
In 1710, the castle was taken over by Carl Piper and Christina Piper. Ängsö Castle was owned by the Piper family from 1710 until 1971, and is now owned by the Westmanna foundation. The castle building itself was made into a museum in 1959 and was made a listed building in 1965. It is currently opened to visitors during the summers.
The castle is a cubical building in four stores made by stone and bricks. The lower parts is preserved from the middle ages. It was redecorated and expanded in the 1630s. The 4th storey as well as the roof is from the expansion of Carl Hårleman from 1740-41. It gained its current appearance in the 1740s.