A wooden fortress originally stood at the site of the present Poděbrady Castle. King Ottokar II of Bohemia replaced it by a stone castle, which became the seat of the Lordship of Poděbrady. King John of Bohemia pledged the Lordship and the Castle to Hynek of Lichtenburg in 1345. When in 1350, Hynek's daughter Eliška married Boček I of Poděbrady (d. 1373), the castle came into the possession of the Kunštát family. After Emperor Charles IV gave Poděbrady to Boček as a hereditary possession, Boček called himself Boček of Poděbrady, thereby founding the Poděbrady line of the Kunštát family.
According to legend, King George of Poděbrady, Boček's grandson, was born in the castle. After George's death in 1471, the Castle and Lordship of Poděbrady were inherited by his son, Henry the Younger of Poděbrady, whose heirs had to transfer ownership of both the castle and the lordship to King Vladislaus II in 1495. Both were pledged several times before the loan was repaid by King Ferdinand I. They remained in the possession of the Bohemian Crown until 1839.
The castle was rebuilt several times. Between 1548 and 1580, it was reconstructed to a Renaissance style, after a design by Giovanni and Ulrico Aostalli and Hans Vienna. After the Thirty Years' War, the castle lost most of its importance. In 1723 and 1724, it was reconstructed in a Baroque style under the direction of the builder Franz Maximilian Kanka. Further modifications were made after 1750. Maria Theresa, in her capacity as Queen of Bohemia, stayed at the castle on several occasions. Under her son Joseph II, the castle was the residence of retired Imperial Army officers.
In 1839, the Crown sold the Castle and the Lordship to the Viennese banker Georg Simon Sina (1783–1856). Through marriage, the castle came into the possession of the Counts of Ypsilanti in 1884.
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.