Mont-Dauphin is one of the many places fortified by Vauban in the second half of the 17th century. Following invasions of Provence by Savoy in 1691 and 1692, Louis XIV dispached Vauban to put the frontier in a better state of defence. In 1692 he came to the Plateau de Mille-Aures, which overlooks both of the invasion routes used by the Savoyards, to fortify it.
The ground in question was on a high hill, roughly four-sided and only readily accessible on one side, another side being steep but passable and the further two sides being cliffs. This meant that the place would only require a short amount of bastioned front, the remainder only requiring a basic wall. The plateau was previously uninhabited, so it was decided that a new town would be built within the fortifications. Plans were made for a front of three arrow headed bastions and two demi-lunes in the north, where the defences were most approachable.
To the south, Vauban planned a trace of smaller bastions, this approach being all but inaccessable. The entrance here was carried over a small demi-lune. Later in the 18th century, the trace of the southern defences was altered, but this demi-lune remained, leaving it oddly skew from the wall. There were serious problems obtaining enough stone for revetting the ditches and ramparts. Thirdly, the threat of invasion from Savoy subsided before the fortifications were completed and the fortress lost its immediate importance. Despite this, Mont-Dauphin was strengthened after French troops suffered a defeat nearby in 1745. For the rest of the century, the barrack buildings multiplied, but some elaborate and extensive plans for extra layers of defence drawn up in 1747 were shelved.
One of the additions that was actually realised is a lunette called the lunette d'arçon, which is an advanced work in the north, but is connected to the fortress by an underground passage. The fortifications at Mont-Dauphin are in very good condition.
In 2008, the place forte of Mont-Dauphin, was listed as a UNESCO World Heritage Site, as part of the 'Fortifications of Vauban' group.
References: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.