Hovgården is an archaeological site on the Lake Mälaren island of Adelsö. During the Viking Age, the centre of the prospering Mälaren Valley was the settlement Birka, founded in the mid-8th century and abandoned in the late 10th century and located on the island Björkö just south of Adelsö. Hovgården is believed to have been the site from where kings and chieftains ruled the area. Hovgården, together with Birka became a UNESCO World Heritage Site in 1993.
The oldest archaeological remains on Adelsö, found north of Hovgården, are grave fields and burial mounds from the Bronze Age (c. 1800-500 BCE). Apparently this culture survived into the Iron Age (500-800 CE) as graves from the early part of this period have been found at several locations in the area. At Hovgården some 124 graves have been found; the oldest from late Roman Iron Age (1-400 CE) and the youngest from the beginning of the Middle Ages (c. 1050-1520), indicating the area has been settled uninterruptedly throughout this period.
Just north of the parish church are five large burial mounds of which three are called Kungshögar. In Swedish, Kung meaning King and högar, from the Old Norse word haugr, meaning mound or barrow. Hovgården apparently was the location for a royal estate Kungsgård as early as the Viking Age (c. 800-1050 CE). An excavation of one of these royal mounds in 1917 revealed the remains of a wealthy man who lived around 900 CE. He was burned lying in a boat, dressed in expensive clothing but without weapons, accompanied by horses, cows, and dogs.
Birka, the oldest town in Sweden, was an international trade post. It has been assumed the royal settlement at Hovgården was established as the king's mean of controlling Birka. However, while Birka was abandoned in the mid-10th century, the royal estate was apparently not as the runestone U 11 from around 1070 which claims to have been carved for the king was erected next to the royal mounds. It was part of Uppsala öd, a network of royal estates supporting the Kings of Sweden.
Furthermore, King Magnus Barnlock had the old castle replaced by a palace built in brick, Alsnö hus, in the 1270s. In the palace, the king established the Swedish nobility through the Ordinance of Alsnö (Alsnö stadga) in 1279. However, the palace was destroyed before the end of that century, and as it was left to decay Hovgården lost in importance.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.