In 1229 the bishop’s residence was ordered moved to a more suitable place at the mouth of the Aura, and it came here — to the spit of land between the Aura and the Vähäjoki. For seventy years Koroinen was the ecclesiastical and administrative centre of Finland, and its bishops effectively governed the country. In 1300 the seat moved about two kilometres downstream to the newly consecrated cathedral, and this became a field.
What is on the ground is the plan of that establishment: the foundations of the church, of the bishop’s castle and of the sacristan’s house, and a cemetery holding more than three hundred graves. Three bishops are buried here; the last of them, Catillus, died in 1286. A white memorial cross stands where the church stood — it was put up in the early 1950s, so the cross is a monument, not a relic.
The archaeology is the interesting part. Excavations at the turn of the 20th century produced close to three thousand finds: coins, mostly Gotlandic, pottery, window and vessel glass, a brick altar, the base of a font, and the remains of a hypocaust heating system — a heated room, in 13th-century Finland, which tells you what kind of household this was. There was further work in the 1970s, and a new campaign ran in June 2026 looking for the bishop’s manor beside the church. The site has been legally protected as an ancient monument area since 1905.
It is also well placed. Koroistenniemi sits within about two kilometres of all three surviving medieval churches of the Turku area — the cathedral downstream, St Mary’s at Maaria to the north-east and St Catherine’s at Nummi to the south-east — and local accounts say all three can be seen from the headland on a clear day.
Be honest about the visit. There is no building, no ticket office, no café and no season. There is grass, stone footings and a cross, reached on the Aura riverside path, about half an hour’s walk up from the cathedral. If you have read anything about the Finnish church in the 13th century it is where the thing began. If you have not, it is a river meadow.
