The Onze-Lieve-Vrouwetoren ('The Tower of Our Lady') is a Late Gothic church tower which is 98.33 metres tall and reaches high above the inner city. It's one of the most eye-catching monuments in town and the third highest church tower in the Netherlands. The church that belonged to the tower was destroyed by a gunpowder explosion in the 18th century.
The first chapel on site was constructed on this site in the 14th century. In the 15th century the chapel was replaced by new church with three aisles. When the tower was built is not exactly known. Construction started around 1444 and was finished around 1470. The official documents of the construction were destroyed by the Protestants in 1579 during the reformation and the ensuing iconoclasm. The church and tower were taken over by the Protestants and no longer belonged to the Catholics.
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.