The Romanesque Abbey church was constructed in the mid-11th century and contains many beautiful 11th- and 12th-century murals which are still in a remarkable state of preservation. It has been a UNESCO World Heritage Site since 1983.
The cruciform church carries a square tower over its crossing. The transept was built first, then the choir with its ambulatory with five radial chapels in the polygonal apse. In the next building campaign, three bays of the nave were added, the bell tower and its porch, and finally the last six bays of the nave. The bell tower is finished by a fine stone spire more than 80 meters high, added in the 14th century (and restored in the 19th century).
The barrel vaulted nave is supported on magnificently-scaled column with foliate capitals.
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.