In the 1280s the king of Sweden’s men start building on a small rocky island at the mouth of the Aura. Twenty years later there is a castle by the sea, a cathedral on the hill and a town between them. Southwest Finland now belongs firmly to the Swedish kingdom.
Why a castle, and why here?
- The Crown moves in. In the late 1200s the Swedish kings tighten their grip on Finland. They need a base that is theirs, not the bishop’s or the local chieftains’. The castle becomes the Crown’s administrative fortress in the region Well documented.
- The site. A rocky island at the river mouth is easy to defend. From it you can watch every ship that comes in from the sea, and the boats heading upriver to the market Well documented.
- A ring of castles. Turku Castle guards the southwest. Häme Castle is built in the interior in the late 1200s, and Vyborg Castle in 1293 on the eastern frontier facing Novgorod Likely. Together they hold the new Swedish lands.
- Part of a boom. Between about 1250 and 1320 some 24 towns and 13 royal castles were founded in the Swedish kingdom, Turku and its castle among them Well documented.
- Wood first, then stone. The castle starts as a small, partly wooden fortress. Over the next two centuries it grows into a great stone castle. The walls and staircases still show the building phases Well documented.
Castle, cathedral, town
The castle is one of three new things that appear at the Aura in a single generation.
- The town. Current estimates put the founding of Turku between 1280 and 1300. It grows up a few kilometres upriver, around a market and the hill where the cathedral is being built Likely.
- No founding charter. No document founding the town survives. One theory says the king, the bishop and the Dominican friars, who came to Finland in 1249, planned the town together. A newer one stresses the merchants: digs have found a 1200s settlement with imported pottery south of the later market square, so trade may have come first Debated.
- 1300 or 1310? A chronicle of the bishops written in the 1570s says the cathedral moved to Turku in 1300. A Dutch text from 1681, found only recently, says the town was founded in 1310 Debated.
- First traces on parchment. The town has a seal by 1309, and a town council and mayors appear in documents from 1323–1324 Well documented.
- The cathedral is consecrated in 1300, and the bishop moves in from Koroinen. That is the next stop.
Who ran the castle?
The king appointed a castle commander (in Swedish hövitsman). He collected the Crown’s taxes, judged disputes and led the troops of the whole castle province. Taxes were mostly paid in kind: grain, butter, fish and furs went into the castle storehouses Likely.
- Lyder van Kyren, a knight from Holstein, held the castle in 1315–1322. In 1318 he defended it against the Novgorodians (stop 5) Well documented.
- Mats Kettilmundsson held a knightly court at the castle in the 1320s: an early taste of the castle as a place of power and display Well documented.
- Many commanders were foreign knights or great Swedish lords. In 1359 even the bishop, Hemming, ran the castle for the king.
No document records the day the castle was founded. The date “c. 1280” comes from building research: archaeologists and architects read the walls, the joints between old and new masonry and the finds in the soil. The picture keeps changing. In 2026, digging for new streets in the harbour area turned up finds that, according to the city, give new information on the castle’s history. The results had not been published in detail when this page was written.