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 Citadelle of Quebec is an active military installation and official residence of both the Canadian monarch and the Governor General of Canada. It is located atop Cap Diamant, adjoining the Plains of Abraham in Quebec City. The citadel is the oldest military building in Canada, and forms part of the fortifications of Quebec City, which is one of only two cities in North America still surrounded by fortifications, the other being Campeche, Mexico.
The first fortifications in Quebec were built by the Governor General of New France Louis de Buade, and completed just in time for the Battle of Quebec in 1690.
After the British conquest in the second half of the 18th century, the problem of Quebec City's defences grew more acute.