The city of Soria formed in a valley near the castle that defended the Douro Riverbanks on the border between the Crowns of Aragon and Castile. The city was destroyed towards the end of the 12th century when Sancho of Navarre attacked it, therefore a great defensive wall was built to prevent further destruction. The wall defended a surface of 100 hectares that went from the Douro River up to the pastureland known as “La Dehesa”, and also from the castle up to the hill where you can find the Chapel of El Mirón.
The Sorian wall was destroyed by General Durán at the end of the Spanish Independence War to avoid French troops from entrenching in the castle. This is the reason why there are so few remains of this castle and why we can only see part of the tower and some parts of the defensive walls. From the castle, you can see a 360º view of the city and the bridge that crosses the Douro River, and in the Chapel of San Saturio, you can see frescos depicting the castle as it once was.
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.