Kalmar Church was built of granite in the late 12th century. Around 1300 it was enlarged and modified to the aisleless Gothic church. In 1485 famous Albertus Pictor decorated walls and vaults with murals. Frescoes were restored in 1958 and still visible. Th current tower was added in 1830. There is font with a cuppa, made of red sandstone, from the late 1100s and medieval wooden sculptures (like a triptych from the mid-1400s) in the church.
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.