St. Hans and St. Peter churches were built side by side during the 1200s. St. Peter was consecrated to the apostle Peter. St. Hans, which was the larger church, was dedicated to St. John the Evangelist. It was where the Lutheran doctrine for the first time preached on the island. In 1527, however, Bishop Brask turned Lutherans out from the church. But as soon as the bishop sailed to Denmark, Lutherans worships were started again. Churches were demolished in 1600-1800s and the stone was used among others to construct Lythbergska house. In 1982 a beautifully decorated gravestone was found in the ruins of in St. Hans, dating from 1050s.
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.