Stora Sundby castle was mentioned first time in Middle Ages. In 1364 it was besieged and captured by Albrecht during his battle with Magnus Eriksson. From the end of 1300s to the early 1400s it belonged to Lars Ulfsson Blå. After him Stora Sundby was owned by Julita monastery and families of Natt och Dag, Sparre and Chevron.
The present main house was built by Lars Siggesson Sparre, who asked Carl de Geer to design a new castle on the old Norman style. The casle was finished in 1848. The drawings were made up by the English architect J.F. Robinson. In refurbishment underwent castle a fundamental change in the exterior but the interior remained mainly unchanged. The architecture symbolizes a year calendar: 52 rooms (number of weeks per year), 12 small towers (12 months per year), four large towers (four seasons), 365 windows (days per year).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.