Nesactium was an ancient fortified town and hill fort of the Histri tribe. In pre-Roman times, Nesactium, ruled by its legendary king Epulon, was the capital of the tribal population of the peninsula called Histri, who were also connected to the prehistoric Castellieri culture. Some theories state a later Celtic influence, but who they were and where they came from has never been discovered for certain. It is believed that their main economic activities were trade and piracy all over the ancient Mediterranean Sea.
In 177 BC, the town was conquered by the Romans and destroyed. Rebuilt upon the original Histrian pattern, it was a Roman town until 46–45 BC, when the Ancient Greek colony Polai was elevated to Pietas Iulia, today Pula. The town was located on the ancient road Via Flavia, which connected Trieste to Dalmatia. The area was abandoned by the Romans in the 6th century, following the Slav invasions.
At the end of the fourth century, the walls were renewed. Two churches were added, next to each other, between the bathhouse and the forum. The southern one, the largest, was probably dedicated to Mary and used for the daily ceremonies; the northern one was used for baptisms and religious ceremonies. There are traces of fire, which may have something to do with the Avar attacks on Histria in 600 and 611.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.