The Ronde Lutherse Kerk or Koepelkerk is a former Lutheran church designed by Adriaan Dortsman (ca. 1636-1682). It was opened in 1671. The organ was built by J Batz in 1830 and it was restored in 1983 by Flentrop Orgelbouw. In 1882 it was rebuilt after a fire. In 1935 the Lutherans left the building and it became a concert hall.
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.