"Turku Castle was founded on an island on the estuary of Aurajoki River in the 1280s as the administrative castle of the Swedish Crown. The castle was originally built in the form of a rectangular fortified camp. The fortified camp became a closed castle in the early 14th century, and the castle was divided into a main castle and bailey. Under the Swedish Duke Johan between 1556 and 1563, Turku Castle was renovated into a handsome renaissance castle; this is when its main features became the size they are today.
In the 1630s the bailey became the official residence for Pietari Brahe, the governor general of Finland. In the late 18th century, after the county governor and Higher Regional Court had moved from the castle to town, the castle underwent significant changes. The bailey became a prison and the main castle became a granary. The castle functioned as a prison until the 1890s after which the historical museum was placed in the bailey. Turku Castle was badly damaged by the bombings in 1941. The fully repaired castle was opened to the public in 1961.
Turku Castle is a significant landmark at the mouth of Aurajoki River, and it is surrounded by the harbour and the small-scale industry and strorage areas that go with it. The Castle is part of the Finnish cultural and architectural heritage as an architectural monument, a museum and as premises for distinguished celebrations.
The Castle has been rented to Turku City for the use of Turku Provincial Museum." - in: www.nba.fi/en/turku_castle