Church of St. Donat (originally Holy Trinity) is the most valuable monument of pre-Romanesque architecture of the early Middle Ages (9th century) in Croatia and a symbol of the city of Zadar, and due to its peculiar shape, it is one of the most significant of its kind in Europe.

According to the type of construction, it follows the forms of court churches with a circular floor plan from the early Byzantine to the Carolingian period. Nevertheless, due to its rough monumentality (height 27 and width 22 meters), unusual cylindrical shape and double interior space, it stands out for its originality, without any direct models. According to tradition, it was built by the Zadar bishop St. Donat in the 9th century, and it was mentioned in the 10th century in his famous work “On State Management” by the Byzantine emperor Constantine Porphyrogenet. It was originally dedicated to the Holy Trinity, and the name St. Donat began to be called Donat only in the 15th century.