The History of Turku Castle
From a 1280s camp castle on a rocky island to Duke John's Renaissance court, the bombs of 1941 and a fifteen-year rebuild — seven centuries in one building.
Turku Castle's construction began in the 1280s, on a rocky island at the mouth of the Aura river chosen because it suited defence. The Finnish Heritage Agency records it as the oldest of the Swedish Crown's castles in Finland; the museum describes it as one of the country's oldest and largest medieval buildings. Across seven centuries it has been a camp castle, a Renaissance ducal court, a courthouse, a barracks, a grain store, a prison and a museum — and it was very nearly destroyed in 1941. This guide traces that sequence period by period.
How did Turku Castle begin?
Construction began in the 1280s, on what was then a rocky island at the mouth of the Aura river, strategically suited for defence. It was founded as an administrative fortress of the Swedish Crown, at a point when Finland was governed as part of the Kingdom of Sweden and Turku was its administrative and religious centre. The first structure was not the closed castle you see today: the Finnish Heritage Agency's register describes an open "camp castle" (leirilinna), a perimeter wall with two towers, later converted into a closed castle divided into a main castle (päälinna) and a bailey (esilinna). That division has governed the building's whole subsequent history — where the state rooms went, where the guns went, where the prison went.
The castle acquired a courtly function early. In the early 14th century the commander Mats Kettilmundsson held a knightly court at Turku Castle, and by the 15th century it was a key fortification in the eastern part of the Kalmar Union, the dynastic union that joined Denmark, Norway and Sweden. Its position was the whole point: at the river mouth it controlled the approach to Turku, the seat of both the Swedish Crown's administration in Finland and the bishopric. The Finnish Heritage Agency today designates the site as a nationally significant built cultural environment (RKY), a listing that covers not just the castle but the 16th-century moat and four merchant warehouses of the 1880s.
How did the medieval castle develop?
The 1300s and 1400s turned a perimeter fort into a stone castle with genuine interiors. Three vaulted rooms date from this phase and survive as named spaces: the Kuninkaansali (King's Hall), the Nunnakappeli (Nun's Chapel) and the Herrainkellari (Gentlemen's Cellar). In the 1480s governor Sten Sture the Elder built the upper levels of the eastern tower and the Sturenkirkko, the Sture Church. By the end of the medieval phase the castle had reached broadly the dimensions it holds today: 120 metres of castle wall, three metres thick, with a West Tower of 38 metres and an East Tower of 32 metres, and 164 rooms in all. The fabric is grey stone.
What that period produced is a defensive building rather than a residence, and the physical evidence is still the first thing a visitor notices. The stairs are steep, the doorways can be narrow, and the courtyard that leads to the entrance is paved with uneven natural stones — none of this is preserved atmosphere, it is what the building was for. The medieval half is also where the exhibition Echoes and Shadows now runs, following the route through the keep and covering the 1300s to the 1600s through the people who lived and worked there: the housekeeper Brita Olofsdotter, Sofia Gyllenhielm, the resistance leader Jaakko Ilkka and King Gustav Vasa among them. Its method is deliberately spare: shadows cast fleetingly on the walls, brief silhouettes rather than reconstructed rooms.
Why did the castle become a Renaissance palace?
Because it stopped being needed as a fortress. Defence was progressively moved outward from the medieval main castle to the bailey and the earthworks, and once the main castle had lost its military significance it could be converted into a Renaissance residential palace. This is the point most often reported backwards: it was the main castle, not the bailey, that became the palace. The renovation ran from 1556 to 1563 and added a new King's Hall to the north wing along with the central staircase tower. The bailey meanwhile gained a round artillery tower at its south-east corner, built between 1568 and 1574 — the military function relocating outward exactly as the residential function moved in.
The court that occupied it belonged to Duke John. Gustav Vasa appointed his son John Duke of Finland in 1556, and the castle's own history records that court life was at its most splendid during Duke John's time — the same years as the Renaissance renovation. John later became King John III of Sweden. His consort was Catherine Jagiellon, and his illegitimate daughter Sofia Gyllenhielm is among the figures the castle's exhibitions name. Duke John and Catherine Jagiellon both appear today as life-size wax figures in The History of Turku Castle exhibition in the bailey, alongside the Turku merchant Valpuri Innamaa. That exhibition, which holds almost 1,000 objects, takes the shift from defensive fortress to Renaissance palace as its organising theme.
What happened after the royal court era?
The castle spent the next three centuries in steady administrative decline. From 1597 it served as an administrative residence; a courthouse function followed from 1623; and in the 17th century it became the residence of the governor. That century is significant enough to the building's story that the museum's permanent exhibition centres a scale model on the castle as it stood in Per Brahe's time, showing 17th-century halls, kitchens and even a sauna. By the 18th century the uses were frankly utilitarian: barracks, warehouse and grain storage. A building raised to project the Swedish Crown's authority into Finland had become, in practical terms, infrastructure. The museum's own exhibition frames the sequence in exactly those terms — the castle as a defence fortification, a transit point for merchandise, a barracks and finally a museum.
The last and longest of those secondary uses was penal. Prison use at the castle ran from the 1770s until 1890, and in the 19th century the outer bailey was specifically converted into a prison. It is worth being precise about this, because the castle's prison era attracts more embroidery than it warrants: the documented facts are the dates and the location in the outer bailey. There is no visitable underground dungeon route at Turku Castle, and the period is interpreted through the exhibitions rather than through a physical circuit. The prison closed in 1890, by which time the building had already begun a second life. The permanent exhibition in the bailey now carries the whole span, from the 13th century to the present day, across almost 1,000 objects, some of them previously unknown finds from the castle itself.
When did Turku Castle become a museum?
A museum was established in the castle in 1885 — over half a century before the war damage, which is worth stating plainly because the post-war restoration is often mistaken for the museum's origin. The Finnish Heritage Agency's register dates museum use from 1890, the same year the prison closed, so the two sources differ by five years; the safest formulation is that the castle became a museum in the 1880s. The four merchant warehouses that stand on the site date from the same decade. Today the museum is part of the City of Turku's museum services (Turun museokeskus), and it holds five exhibitions across the main castle, the bailey and two attic halls.
It is now the most-visited museum in Turku, though not in Finland — a distinction worth keeping straight. In 2025 the castle recorded over 123,000 visits, of which nearly 103,000 were paid admissions, while the City of Turku's museums together passed 650,000 visits in the same year. The castle is also a Museum Card (Museokortti) destination, and the card recorded 2.5 million museum visits nationally across 2025. The Finnish Heritage Agency's RKY listing designates the site as a nationally significant built cultural environment, which is the formal protection status behind the way the building is now conserved and interpreted. The museum opens Tuesday to Sunday and is closed every Monday of the year, running 10:00–18:00 from 1 June to 30 August 2026 and 10:00–17:00 from 31 August.
How was the castle rebuilt after 1941?
The main castle was severely damaged during the bombings of 1941. Restoration had officially started in 1939 — plans had been discussed since the late 19th century — but the Winter War interrupted it, and the work that mattered ran from 1946 to 1961. The chief architect was Erik Bryggman, and the interior architect Carin Bryggman continued his work. The guiding principle was stated clearly: preserve all surviving structures and reconstruct only those elements for which there was reliable evidence. It was described as the largest project of its kind undertaken in the Nordic countries at the time, and the whole programme ran for roughly fifteen years before the castle reopened.
Bryggman did not restore the building to a single moment. He added frankly modern elements — new staircases, new exhibition spaces in the attic, and concealed technical services — which is why the Northern Exhibition Hall exists at all, an almost 60-metre-long attic space with no medieval equivalent. The most contentious decisions were the reconstructions of the castle church and the medieval King's Hall. Renovation and restoration were completed in 1961, and further comprehensive phases followed between 1975 and 1993. The whole argument is now on display in its own right: "Built from Ruins", in the Southern Exhibition Hall on the 6th floor, documents the 1946–1961 project.
Frequently asked
When was Turku Castle built?
Construction began in the 1280s on a rocky island at the mouth of the Aura river. The Finnish Heritage Agency records it as the oldest of the Swedish Crown's castles in Finland, and the museum calls it one of the country's oldest and largest medieval buildings.
Who built the Renaissance parts?
The main castle — not the bailey — was converted into a Renaissance palace in the renovation of 1556 to 1563, during Duke John's time as Duke of Finland, adding a new King's Hall to the north wing and completing the central staircase tower.
Who was Duke John?
Gustav Vasa appointed his son John Duke of Finland in 1556; he later became King John III of Sweden. The castle's history records that court life there was at its most splendid in his time. His consort was Catherine Jagiellon.
Was Turku Castle damaged in the war?
Yes. The main castle was severely damaged in the bombings of 1941. Reconstruction ran from 1946 to 1961 under the architect Erik Bryggman, with interior architect Carin Bryggman continuing his work, and further phases followed between 1975 and 1993.
Was the castle ever a prison?
Yes. Prison use ran from the 1770s until 1890, and the outer bailey was converted into a prison in the 19th century. There is no visitable underground dungeon — the period is interpreted through the museum's exhibitions.
When did it become a museum?
A museum was established in the castle in 1885, according to its own history page, while the Finnish Heritage Agency's register dates museum use from 1890. Either way, the museum predates the war damage by more than fifty years.
What else has the castle been used for?
An administrative residence from 1597, a courthouse from 1623, the governor's residence in the 17th century, and barracks, warehouse and grain storage in the 18th century, before its long spell as a prison.