Shortly after the Romans founded Cologne in 50 AD, they built a wall around the city. The wall was first expanded in the tenth century, and again in 1106, but due to the continuing growth of the city a new, 7 meters high wall was built in the twelfth and thirteenth centuries.
The most important of the twelve gates that gave entrance to Cologne was the west gate, known as the Hahnentor. After their coronation in Aachen, German kings arrived in Cologne through this gate to revere the shrine of the Three Magi in the Cologne cathedral. The gate was built between 1235 and 1240 and was probably named after a citizen named Hageno, who owned the nearby land.
The Hahnentorburg has two semi-circular, crenellated towers. The city's coat of arms is depicted above the entrance. The tower was restored in 1890 by the city architect Josef Stubben; a memorial plaque commemorates the architect's construction of Neustadt (new city) between 1881 and 1898 outside the former city walls. The tower was severely damaged during the Second World War, but was later reconstructed.
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.