The Barbican, the 15th century bastion with a circular floor plan used to belong to the wall system of the Bishop's Castle. Its construction is linked to the visit of General Pál Kinizsi, who came to the town in 1498. In the shadow of the Turkish threat the defence systems of castles and towns were strengthened all around the South. The Gothic-style gate tower was built in the 15th century at the western corner of the high castle wall. The Barbican is a round gate tower sitting on a narrow column. Its back gate served a specific purpose: it enabled the defenders to attack the attacking enemy getting in the gate from the side. The Barbican is surrounded with the remains of the castle ditch and you can walk up to the entrance on the old drawbridge. The pulleys of the drawbridge are still displayed inside.
There is a fantastic view opening towards the town from the top of the bastion. You can walk along the machicolation (the wooden walkway) on the top of the Barbican.
After defence structures became obsolete during the 18th-19th century, similarly to other parts of the town, houses were built around the castle wall. The buildings that were built along the castle walls were demolished in the 1960s making the old Barbican as well as other parts of the wall free and visible again.
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.