The construction of Don Álvaro de Luna castle was commissioned by the High Constable Ruy López Dávalos between the end of the 14th century and the beginning of the 15th century.There is very little left in the interior of the castle. The fires originating from the different wars have left, over time, only the walls of the building. In other periods it was used as a prison and cemetery, and today it is the municipal auditorium.
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.