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. It has three radially situated apses and an ambulatory around the central area, surmounted by circular gallery. The circular shape is typical of the early medieval age in Dalmatia. It was built on the Roman forum, and materials from buildings in the latter were used in its construction. Among the fragments which are built into the foundations it is still possible to distinguish the remains of a sacrificial altar on which is written IVNONI AVGUSTE IIOVI AVGUSTO.
The use of the church has varied during its lifetime; during the rule of the Republic of Venice it was a warehouse, as well as during the French occupation and under the Austrians. After the city was annexed to Yugoslavia, it served as an archaeological museum for a short period of time. The building is currently used as the concert venue for the annual International Festival of Medieval Renaissance Music due to the building's interiors and acoustics.
References:Bomarsund fortress and garrison was built in 1832-1854 by Russian Empire to defence Åland Islands against enemies. British and French fleet attacked against it during the Crimean War in 1854. After a week of fighting the British stormed the remaining fort. Anglo-French forces destroyed it totally after battle. In the Treaty of Paris 1856, the entire Åland Islands were demilitarized, which is a status that has been preserved until this day.
Nowadays there are some ruins left and fortress area is open for visitors.