The Abbey of Nivelles was a former Imperial Abbey of the Holy Roman Empire founded about 648-649 AD by the widow of Pepin of Landen, Itta of Metz, along with her daughter, Gertrude of Nivelles. The abbey began as a community of nuns; they were joined later by Irish monks from the Abbey of Mont Saint-Quentin, sent by Abbot Foillan to give support to the nuns. A group of the monks settled at Nivelles and it soon became a double monastery, led either by an abbot and abbess, later only by an abbess. At that point, the abbey came under the influence of Irish monasticism, with its heavy emphasis on a severe asceticism.
In the 9th century there began a process of secularization of the community which possibly ended in the 12th century. The abbey had close ties to the royal family, and played an important role in the social life of the palace. From the 12th century, the character of the community began to change to a more prestigious one, so that the members became canonesses regular who came from among the nobility, as attested in a document dated 1462. For most of the Middle Ages the Abbey remained an Imperial Abbey, a semi-sovereign institution directly under the king.
The abbey was suppressed after the invasion of the Duchy of Brabant in 1794 by the armies of the First French Republic.
The old abbey church, which became the Collegiate Church of Saint Gertrude under the canonesses, was gutted by aerial bombs dropped by the German Luftwaffe in May 1940 during the Battle of Belgium, but it was restored to its 11th and 13th centuries form after World War II. The site was excavated in 1941 and 1953.
Today the basement of the old abbey holds a number of artifacts and a rich archaeology and is open to the public. The adjoining Romanesque-Gothic cloister dates from the 13th century. A procession is held every year on the Sunday after Michaelmas.
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.