The Château du Landsberg in Heiligenstein includes a Zwinger with two sets of defensive walls. The central part of the castle was built in the late 12th century, and the newer outer castle added onto at the start of the 13th century by Conrad de Landsberg to provide defence for the abbeys of Mont Sainte-Odile, Niedermunster, Truttenhausen and Andlau. More recent additions were made in the 15th century. Herrad of Landsberg was born here around 1130. The castle is privately owned.
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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.