Count Wilhelm II of Katzenelnbogen built the Katz Castle in the second half of the 14th century. Katz Castle was used as bastion and military base to protect the Rheinfels Castle. Together they formed a fortified bulwark with a barrier for levying of the Rhine toll. The extended view up to the bend of the river at the Loreley was also of great importance to secure salmon fishing. Due to the intentionally chosen location on the mountain ridge Katz Castle could not possibly be conquered from the valley.
Only after the invention of fire arms, Katz Castle had to be substantially reinforced. It was also upgraded as bastion against Maus Castle in the Electorate of Trier. At the same time the donjon of Katz Castle was raised to to ensure eye contact with Reichenstein Castle. In 1479 the family line of the Counts of Katzenelnbogen died out.
In succession of long-lasting disputes on heritage, Katz Castle and Rheinfels Castle were besieged, demolished, rebuilt and extended several times. Even though repairs had been made in 1800, Napoleon blew up Katz Castle in 1806.
In 1896 District Administrator Berg acquired Katz Castle, to reconstruct it as close as possible to the original design. From 1946 till 1951 Katz Castle served as local High School 'Institut Hofmann' including board
Since 1989 Katz Castle is private property of a Japanese and accommodates the hotel Katz Castle.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.