The Church of St. Donatus in Zadar, a medieval monument from the 9th century, built on the remains of the Roman Forum. In its beginnings it was dedicated to the Holy Trinity, to later take the name of Bishop Donatus, who oversaw the construction of the church.In its present form, the church is structured as a cylinder within a cylinder. The outer wall connects with the inner wall on the first floor creating a gallery in the inner cylinder. The interior is finished with a conical roof supported by six pilasters and two pillars that were part of the original Roman forum. The theme of the Holy Trinity is reflected in the three apses and three doors of the church.For centuries, the Church of St. Donatus has changed its purpose from secular to religious and vice versa. Until 1956, it served as a military warehouse, wine cellar, and archeological museum. Due to its excellent acoustics, today it serves as the main place in Zadar for concerts and recitals and other cultural and artistic events.