Seili (Själo in Swedish) is a small island in the Archipelago Sea. The island is known for its church and nature, a research institute and a former hospital. The first hospital on Seili was established in the 1620s. Before that there were two farms on the islands belonging to the Crown and thus available when the authorities looked for a suitable island to which the leper hospital at the outskirts of Turku could be moved.
According to a Royal Decree in 1619 by King Gustav Adolf of Sweden, the buildings of the hospital in Turku, with the exception of the chapel, were burned down and the inmates transported to Seili. The Selihospital for lepers was dedicated to St George. The last leper patient died in 1785, and the establishment on Seili became a hospital or a place of confinement for mentally afflicted people until 1962. The hospital was self-sufficient with agriculture, and fishing. The present-day buildings on the island, with the exception of the chapel, date from the 19th and the 20th centuries, and most of them have been built for the mental hospital.
The wooden chapel of Seili was built in as a replacement of the Church of Saint George, the former hospital church which had been transferred to Seili from Turku in the beginning of the 17th century. The museum church has a cross-shaped plan and it is made of pinewood grown in archipelago islands. The original untreated wooden surface can still be seen inside the church and nowadays it is beautifully patinated by passed centuries. The only colourful objects in the otherwise quite barren but impressive interior are the pulpit decorated by C.J. von Holthusen and the modernistic altarpiece The Storm on Lake Genesaret painted by the Finnish artist Helge Stén.
Currently the island hosts the Archipelago Research Institute that is a part of the University of Turku. The island is open to the public in summertime and there are guided tours available. During the summer season, the connecting ferry m/s Östern operates on the Nauvo-Seili-Hanka (Aasla, Rymättylä) route. Therefore, Seili is accessible from both Nauvo and Hanka.
The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.