The Piarist Church, also known as the Church of Maria Treu, is a Baroque parish church of the Order of the Piarists in Vienna. The church has eight chapels and is decorated with frescoes made by Franz Anton Maulbertsch in 1752–53. Commissioned by the Piarists, Haydn’s Missa in Tempore Belli (Mass in Time of War, sometimes known as Kettledrum Mass) was first performed here on 26 December 1796. The Piaristenkirche was elevated to the rank of Basilica Minor in 1949.
References:The Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.