El Fadrí is a standing alone bell-tower of the Gothic procathedral Castelló Cathedral of Castellón de la Plana, Spain. It was built in the 15th century, commencing in 1440 and completed in 1604. It is an octagonal building, about 58 metres high. It was built in Valencian Gothic style. A discontinuous spiral staircase gives access to the clock chamber, the clergyman's cell, the bell ringer's home, and the bell chamber.
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.