The St. Olaf's Church in Tyrvää is a late medieval stone church built probably in 1510-1516. Archeologists have found evidences that the church site has been a spiritual place even in 1000 BC. The settlement has concentrated to the Vanhankirkonnimemi area during the end of Iron Age. There may have been two wooden churches before the present one built in the 14th century. The St. Olaf's Church was probably extended in the 17th century by local family of Nuutila.
When the new wooden church was completed in 1855, St. Olaf's church was abandoded for one hundred years. The church was well known of it's unique interior, until it was burnt down by a pyromaniac in 1997. The church was rebuilt by local people and the interior paintings were created by painters Kuutti Lavonen and Osmo Rauhala.
Finnish National Board of Antiquities has named the church site as national built heritage.
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.