Helsinki Cathedral is a distinct landmark in the scenery of central Helsinki, with a tall green dome surrounded by four smaller domes. It was built in 1830–1852 in neoclassical style to replace an earlier church from 1727. The cathedral was designed by Carl Ludvig Engel, to form the climax of the whole Senate Square laid out by Engel, surrounded by a number of buildings all designed by him.
Today the cathedral is one of the most popular tourist attractions in Helsinki. Annually more than 350,000 people visit the church, some of them to attend religious events, but most as tourists. The church is in regular use for both worship services and special events such as weddings.
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.