The spectacular Kallio church, designed by Lars Sonck and built in 1908–1912, represents the Finnish national romantic school of architecture, as well as a change to Art Nouveau. The bells of the tower play a melody composed by Jean Sibelius. Inside the church are numerous interesting details such as a crucifix and relief made by sculptor Hannes Autere.
In the beginning of independent Finland Tolstoyan movement took the church as their base and proclaimed pacifism there. During World War II the church tower was one of Helsinki's air control points. In good weather, you can see Estonia from the tower.
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.