The Orthodox cathedral was built in 1890-1898 by the Kreenholm manufacture for its Orthodox labour. It was designed by architect Pavel Alisch. The great cathedral is made of brick and Finnish granite and has seats for 2000 people.
The most prominent feature of its interior is the wooden crucifix (Architect Astafjev). The icons were painted by Michail Dickarev (Palech School).
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.