The St. John Fortress is a complex monumental building on the southeastern side of the old city port, controlling and protecting its entrance. The first fort was built in the mid-14th century, but it was modified on several occasions in the course of the 15th and 16th centuries, which can be seen in the triptych made by the painter Nikola Božidarević in the Dominican monastery. The painting shows Saint Blaise, the patron saint of Dubrovnik.
Dominant in the port ambiance, the St. John Fortress prevented access of pirates and other enemy ships. Always cautious at the first sign of danger, the inhabitants of Dubrovnik used to close the entry into the port with heavy chains stretched between the St. John Fortress and the Kase jetty, and they also used to wall up all the port entries to the Great Arsenal.
Today, the fortress houses an aquarium on the ground floor, stocked with fish from various parts of the Adriatic Sea. On the upper floors there is an ethnographic and a maritime museum devoted to the Republic Maritime Period, the Age of Steam, the Second World War, and the section of techniques of sailing and navigation.
References: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.