Built outside the walls to the north of the walled enclosure, San Martín Church has a Roman origin, as confirmed by the latest archaeological explorations. After the Roman building had been apparently ruined, it was rebuilt and radically transformed in the 16th century and at the beginning of the 18th century.
In the 14th century, the tower was built on a base made of granite ashlar work and an upper body made of brick. It also stands as a belfry of Gothic tradition and shows evidence of the Mudejar Masters. The pointed openings are of particular interest and are made of decreasing horseshoe archivolts set in a panel.
In the 16th century, the layout was completed and structured into three naves separated by semi-circular arches. In the 18th century, the Main Chapel was refurbished and the side chapel and semi-spherical cupola above the Presbytery were built. Two Roman altar stones were reused in the south wall.
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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.