The St. Mary's Church in Sønderborg is located on a hill and is a very iconic for the city. In the Middle Ages there was a leper colony on a hill just outside the city. It was named after Saint George and around 1300 the chapel of this leper colony stood in the place of the present St. Mary's Church. After the old parish church of the city, the St. Nicholas Church, was demolished around 1530, the Saint-George chapel became the new main church. Towards the end of the 16th century, John II, Duke of Schleswig-Holstein-Sonderburg commissioned the enlargement of the building in order to make it suitable for the function of the parish church of his city.
In 1595 a start was made on the partial demolition of the old church and the construction of the new church. Only parts of the old medieval church remained. From the medieval church, a medieval wooden wall cupboard dating from about 1400 remained. The solemn inauguration of the new parish church took place just before Christmas in 1600. In 1649 the George Church was renamed as the Mary Church.
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.