St. Mary's Church (Marienkirche) is a large Lutheran church built some time before 1298. It is architecturally Gothic, an example of the brick gothic style prevalent in northern Germany. Between 1625 and 1647, it was the tallest building in the world at 151 metres tall.
The bell tower collapsed in 1382, and was rebuilt by 1478. In 1495, the steeple tower blew down during a severe storm, and was then rebuilt taller. This was subsequently struck by lightning in 1647, and burned down, and was rebuilt as a baroque dome, which, completed in 1708, can be seen today. The tower is currently 104 metres tall.
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.