Turku Castle of grey stone at the mouth of the Auraoki is a prominent landmark, now surrounded by the harbour with its associated light industrial and storage areas. As the oldest of the castles in Finland built under the Swedish Crown, it was founded on an island in the Auraoki in the 1280s, but is mentioned in documentary sources for the first time in 1308. The castle served as the administrative centre of Finland under Sweden and of the province from the Middle Ages into the modern period. In form the castle was originally an open campaign castle with a curtain wall and two towers. From the campaign castle a closed castle was formed in the early 14th century, divided into a main castle and a bailey that gradually developed in front of it. The bailey was first mentioned in documentary sources only in 1463. The vaulted King's Hall, the Nun's Chapel and the Lords' Cellar were built around the turn of the 14th–15th centuries. The regent of Sweden, Sten Sture the Elder, had the two upper storeys of the east tower and the so-called Sture Church built in the 1480s. Gustav Vasa appointed his son John as Duke of Finland, during whose time 1556–1563 the medieval defensive castle was transformed into a Renaissance castle. The court served as the model for Finland's Renaissance era. A new storey was built in the castle for the duke's and his consort's, Polish princess Katarina Jagellonica's, use. The topmost storey of the north wing received a new king's hall and a new stair tower was completed at the centre of the inner courtyard. The comfort of the interiors was enhanced by, among other things, wall panelling, woven tapestries and paintings. The bailey, which functioned as the officials' workrooms, was supplemented and a round cannon tower was built at its south-east corner in 1568–1574. The castle then also reached, in its main features, its present dimensions. The castle was besieged for the last time in 1597–1599, after which it was used as an administrative and residential place. The main castle with its furnishings burned down in 1614 and despite reconstruction, activities moved mainly to the bailey. The Court of Appeal established in Turku in 1623 began operations in the bailey, and the room in the eastern wing became in the 1630s also the official residence of Finland's governor-general Pehr Brahe. Extensive alterations were also made to the castle in 1698 when the governor and the county administration moved to the city. After the castle's administrative function ceased, it became a prison and the Crown's storehouse. The bailey tower was converted into a prison in the 1770s and the entire bailey in the early 19th century. The main castle was used as a granary and other storage. The current castle church was placed in the 18th century in Duke John's former banqueting hall. During the Finnish War the castle was the station of the archipelago fleet's Turku squadron. Museum operations began in Turku Castle's bailey as early as 1881. When the county prison vacated the castle in 1890, the entire bailey was transferred to the historical museum. The castle also contains older premises used as a prison, including the oldest dungeon prison built in the 14th century. The dethroned king Erik XIV was imprisoned in the 1570s in the bailey's rooms together with his wife Karin Månsdotter and his children, and later in the cell of the hexagonal tower. The castle's surroundings have changed since its founding, both due to the development of the urban structure and in terms of topography. The strait between the castle island and the mainland had already closed up during the 16th century, and it has also been filled in since the 19th century. In the castle park area, part of the outer moat from the 16th century is still visible; it was restored as late as the 18th century. A garden was established around the castle already in the latter half of the 16th century. Trees were also planted to line the road leading from the castle to the city, which was probably Finland's first realised park street. In the early 20th century, it was decided to establish an open-air museum in the castle's surroundings. The city park superintendent M. Hammarberg's plan was drawn up and the park with open-air museum was opened in 1906. The open-air museum was discontinued after the wars when some of the buildings were destroyed. The park was renovated around 1920–1930 and in the 1950s. The northern side of the castle along Linnankatu was supplemented in 1888–89 by four warehouse buildings commissioned by merchant C.A. Doepelin, representing the oldest private commercial activity in the harbour area. Research in preparation for the castle's restoration began in 1939, but in summer 1941 the main castle's interior was destroyed in an air attack. The restoration based on Professor Erik Bryggman's plans is considered one of the significant layers of the castle. The restored main castle was opened to the public in 1961. The bailey was restored anew under the supervision of the National Board of Antiquities in 1975–1987 and the main castle in 1986–1993. Most of the castle's rooms with their vaults have been restored to their original appearance from different periods. The castle's current exterior is the result of construction phases from various periods.
Official description (Museovirasto) — machine-translated from Finnish
Turku Castle is a medieval structure in the city of Turku, Finland. Together with Turku Cathedral, the castle is one of the oldest buildings still in use in Finland. It is also the largest surviving medieval building in Finland. It was founded in the late 13th century and stands on the banks of the Aura River. The castle served as a bastion and administrative center in the historical region of Finland until the early 19th century. It played a role in power struggles within Sweden and the Kalmar Union and stood sieges, with additional battles fought outside its walls. The castle was at its peak in the mid-16th century, during the reign of Duke John of Finland and Catherine Jagellon. It lost its status as an administrative center in the 17th century, after Per Brahe's period as governor-general of Finland came to an end. Turku Castle is Finland's most visited museum. Visitations reach well over 100,000 people annually. Some of the rooms in the castle are used for municipal functions.
