St. Gereon's Basilica (Basilika Sankt Gereon) was first mentioned in 612. However, the building of the choir gallery, apse, and transepts occurred later, beginning under Archbishop Arnold II von Wied in 1151 and ending in 1227. It is one of twelve great churches in Cologne that were built in the Romanesque style.
St. Gereon has a highly irregular plan, the nave being covered by a decagonal oval dome, 21.0 m long and 16.9 m wide, completed in 1227 on the remains of Roman walls, which are still visible. It is the largest dome built in the West between the erection of the Hagia Sophia in the 6th century and the Duomo of Florence in the 15th century.
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.