The article says the Swedes built the castle, with the infobox giving the 1300s and the text placing the start of construction in the 1380s. It was first mentioned in a charter of 1388. It is brick and mortar, with a rectangular stone keep and a residential wing, and a 3-meter (about 10 ft) defensive wall. It stood on a small island surrounded by moats. Two gate towers, from the 15th and 16th centuries, were later merged into the donjon called Kurtornet.
Danish forces captured it in 1505, and John III imprisoned Eric XIV there in 1571. Artillery heavily damaged it in 1599. A fire in 1745 destroyed much of it, and it was abandoned in the 1770s.
Restoration and excavations ran from 1982 to 1989. The Government of Åland owns it and runs it as a museum, and a medieval festival is held each July.

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