Between Provence and Dauphiné, dominating the cluse where the Durance flows, the Citadelle of Sisteron dominates the sky, crowning the town with its walls, bastions and keep. The view from here is breathtaking, stretching for 150 km and offering one of the finest vantage points in Haute Provence. It bears witness to eight centuries of architecture and history. The keep and sentry walk, built on the narrow rocky spine, date back to the 12th century. The tiered bastioned enclosures dating from the 16th century of the Vauban project, designed in 1692, only the powder magazine was built.
Major alterations were carried out on the north face in the mid-19th century. It was at this time that the magnificent underground staircase linking the fortress to the town was carved out of the rock.
The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.