San Nicolás de la Villa is one of the twelve Fernandine churches built in the city after its conquest by King Ferdinand III of Castile (1236), in Gothic-Mudéjar style, although it was completed only in the following centuries, with much renovation added in the meantime. The main portal, in Renaissance style, was added by Hernán Ruiz the Younger in the 16th century. The octagonal tower, with a defensive appearance, was rebuilt during the age of the Catholic Monarchs above an older Islamic minaret.
In the 17th and 18th century, much of the church's elements were modified until it received the current mostly Baroque appearance. The baptistery dates from 1555.
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.