According a tradition there has been a defensive complex here since pre-Roman times. The Rocca fortress was built in the late 12th and early 13th centuries. The last military operation took place in 1510 and after that Rocca was moved as hospital and private use.
The fortress was involved in his latest war episode in 1510 . Gradually Persa's strategic importance, the structure was used as a variety of uses also becoming hospital during the continuous plagues of the sixteenth century. Decommissioning in 1650 , Venice even tried to sell it to private.
The massive construction has a polygonal plant of nine unequal sides. There are no open slits or windows: only one door gives an access to the upper defensive system of the city.
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.