The Parish Church of St Clement's origins lie with a privately owned wooded chapel which is thought to have been destroyed during the Norman raids. Construction of the stone church began around the year 911, starting with a chapel which is now the nave. The church became a parish church no later than 1067, because it is known that Duke William II of Normandy granted half the tithes of the church to the Abbey of Montivilliers in Upper Normandy. Only parish churches were permitted to collect tithes.
In the 15th century the church was considerably enlarged by the addition of a chancel and transepts, giving it the usual cruciform shape of most Christian churches. It has been possible to ascertain the approximate date for these enlargements and alterations from the Payn Arms (the three trefoils) in the chancel. The Payns were the Seigneurs of Samares during the 15th century. Also from this period are the gargoyles on the East outside wall, and the murals or frescoes inside the church. When the church was enlarged, the roof was raised and constructed in stone. The line of this may still be observed on the tower arch and buttresses were also constructed to support the weight.
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.