This architecturally unusual church is built in two parts. The main section, the church proper, is approximately a square. The interior is in Baroque style, a trompe-l’œil fantasy in pinks and greys. The ceiling takes the form of a dome, which was painted in fresco in the late 18th century.
In addition to housing Haydn’s tomb, the Bergkirche is notable in the history of music in that it was the scene of the premiere of most of the late masses that Haydn wrote for his patrons during the final phase of his career. Later, Beethoven led the (unsuccessful) 1807 premiere of his Mass in C (again a commission from the Esterházys) in the church.
The church still possesses its original organ, built in the 18th century by the Viennese maker Gottfried Malleck; the instrument has been restored to its original state, as it was when it was played by Haydn and Beethoven at the premieres of famous works.
To the east of the main church is a kind of artificial mountain, the ”Kalvarienberg” (Calvary Hill), which is filled with passages and grottoes, in which appear statuary depicting the 24 Stations of the Cross. The statues, which are vividly, even garishly painted were the work of Franciscan monks, working over 250 years ago. In historical times the Kalvarienberg was a destination for pilgrimages and was regarded as the eighth wonder of the world.