The Oostkerk was designed by Bartholomeus Drijfhout and Pieter Post and was built between 1648 and 1667. After Drijfhout died in 1651, the building was continued under the Leiden architect Arent van 's Gravezande, who had just completed the Marekerk in Leiden. The white organ was built by Gebr. de Rijckere from Kortrijk in 1782. Two stained glass windows from 1664 still exist in the church, and the klokkenstoel contains a bell by C. Noorden and one by J.A. de Grave, 1715.
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.