The St John’s (Jaani) Church of Haapsalu was built during the restless reformation years during the early part of the 16th century (first mentioned in 1524), and initially it was dedicated to St Nicholas. The church is exceptionally laid out in a north-south bearing. The basement of the church was an ancient storage house. The church has a beautiful stone altar (17th century), a wooden pulpit (18th century) and one of the oldest surviving church bells from the 16th century.
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.