St. Casimir’s Church was founded by the Jesuits and dedicated to Lithuania’s patron saint Prince Casimir Jagiellon (1458-1484). The construction of the glorious building began in 1604 and was completed in 1635. Burnt to the ground just 20 years later when the Russians invaded in 1655, conflagration visited twice again within the next century in 1709 and 1749 before the architect, mathematician and astronomer Tomas Žebrauskas (Pol. Thomas Zubrówka, 1714-1758) restored it to more or less the form it's seen in today.
Over the centuries the church fell into the hands of the Augustinians, Napoleon’s Grande Armée, the Russian Orthodox Church (who significantly altered its appearance), the Lutherans (who used it as the garrison church for the occupying German Army during WWI) and others, including the Soviets who turned the whole place into a museum of atheism no less. Returned to the Catholic Church in 1988, the building was consecrated in 1991 and has since undergone a massive renovation project, restoring its predominantly Baroque style with Gothic and Renaissance touches. Of particular interest inside are three late Baroque altars and a recently discovered 17th-century crypt containing dark bas-reliefs featuring miscellaneous religious motifs.
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.