The remains of an assumed 13th-century episcopal church and associated brick structures at the Cape of Koroinen, southwest Finland, were excavated in 1898–1902. The structures may constitute the first occurrence of masonry buildings, and the use of brick in mainland Finland. Such conclusions, however, have also been questioned. The evaluation of the discoveries has been difficult, because the excavation results were never thoroughly published. The present article re-examines the findings, and discusses their importance for the understanding of Koroinen.

The first wooden church at Koroinen had a rectangular nave measuring probably 20 by 10.5 m, and a narrow choir, 4.5 by 4.5 m in size. Inside the choir, a brick altar and brickwalled grave 2 may have been built. The altar foundation measured ca 1.2 by 1.1 m and was possibly erected entirely of bricks. These two structures were mainly constructed of ordinary wall bricks. The nave of the second wooden church measured ca 27.5 by 14.5 m, and it had a narrow choir as well. A brick podium for a baptismal font, as well as a sub-surface drain made mostly of bricks, was presumably connected with the second church. It seems likely that also a brick-walled grave 1 was built into the wooden choir.
The wooden church was located at the same place where a choir of stone was later
built. Apparently the masonry choir represented the first construction phase of a stone
church. It was not planned to be tower-height, and it is not certain whether it was ever
completed. Based on the archaeological finds, it seems that site was no longer used in
the Late Middle Ages.