The Alcazar of Jerez de la Frontera is a former Moorish alcázar, now housing a park. A first fortress was probably built in the 11th century, when Jerez was part of the small kingdom of the taifa of Arcos de la Frontera, on a site settled since prehistoric times in the south-eastern corner of the city. In the 12th century, a new structure was erected to be used as both residence and fortress by the Almohad rulers of southern Spain. Later, after the Reconquista of Andalusia, it was the seat of the first Christian mayors.
Its various parts, which have been magnificently restored, include the Christianised Mosque dedicated to Santa María la Real, the Arabic Baths, the Oil Mill and the beautiful gardens.
The Dark Chamber is located in the tower of Villavicencio Palace (17th-18th centuries) in the Fortress, the oldest monument in this city. The visit includes a ticket for two exhibitions. The first one is about the dark chambers in the world. The second one is a themed exhibition about Jerez, explained by a guide who stands out the most important monuments.
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.