Château de Villeneuve-Loubet, property of the Panisse-Passis family, is a superb 13th-century defensive structure, with a pentagonal keep. It was built in the 13th century, at the instigation of the Counts of Provence and Romeo of Villeneuve. Ramparts and parapet walks are punctuated with five round towers and a mediaeval drawbridge. French King Francis I stayed there in 1538 to sign the Truce of Nice with the Emperor Charles V, a pact which put an end to the Italian Wars.
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.