The Church of Saint Nicholas was built between 1704-1755 on the site where formerly a Gothic church from the 13th century stood. It has been described as the most impressive example of Prague Baroque.
In the second half of the 17th century the Jesuits decided to build a new church designed by Giovanni Domenico Orsi. A partial impression of the original planned appearance of the church at the time the Jesuits chose the initial plans by Giovanni Domenico Orsi in 1673 and laid the foundation stone is provided by the Chapel of St Barbara, which was built first so that mass could be celebrated. The church was built in two stages during the 18th century. From 1703 till 1711 the west façade, the choir, the Chapels of St Barbara and St Anne were built.
The new plans involved an intricate geometrical system of interconnected cylinders with a central dome above the transept. The massive nave with side chapels and an undulating vault based on a system of intersecting ellipsoids was apparently built by Christoph Dientzenhofer. The pillars between the wide spans of the arcade supporting the triforium were meant to maximize the dynamic effect of the church. The chancel and its characteristic copper cupola were built in 1737-1752, this time using plans by Christoph's son, Kilian Ignaz Dientzenhofer.
In 1752, after the death Dientzehofer in 1751, the construction of the church tower was completed. During the years the church continued to expand its interior beauty. Following the abolition of the Jesuit Order by Pope Clement XIV, St Nicholas became the main parish church of the Lesser Town in 1775.
During the communist era the church tower was used as an observatory for State Security since from the tower it was possible to keep watch on the American and Yugoslav embassies respectively and the access route to the West German embassy.
The church excels not only in the architecture, but also in the decoration, mainly with the frescos by Jan Lukas Kracker and a fresco inside the 70 m high dome by František Xaver Palko. The interior is further decorated with sculptures by František Ignác Platzer. The Baroque organ has over 4,000 pipes up to six metres in length and was played by Mozart in 1787. Mozart's spectacular masterpiece, Mass in C, was first performed in the Church of Saint Nicholas shortly after his visit.
The 79 m tall belfry is directly connected with the church’s massive dome. The belfry with great panoramic view, was unlike the church completed in Rococo forms in 1751-1756 by Anselmo Lurago.
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.