First built in 1248 as a Romanesque basilica with a nave and two aisles, the cathedral gained its current appearance in the 15th century as a Gothic structure, though the Baroque chapels date from the 16th and 18th centuries. Inside, one is treated to the sight of a lavishly adorned altar, which lights up the place all on its own.
The 57 metre high classicist designed bell tower dates back to the end of the 18th century as the primarily 76-metre high bell tower built by Pavel Porta in the year 1623 was struck by lightening.
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.