Xanten Cathedral (Xantener Dom) is considered the biggest cathedral between Cologne and the North sea. The cathedral owes its name to Victor of Xanten, a member of the Theban Legion who was supposedly executed in the 4th century in the amphitheater of Castra Vetera for refusing to sacrifice to the Roman gods. This Roman camp is near today's town of Birten. According to legend, Helena of Constantinople recovered the bones of Victor and his legion and erected a chapel in their honour. During a modern excavation the existence of a 4th-century cella memoriae was discovered; however, it was determined that it had not been erected for Victor but for two other male corpses that were placed in the crypt at a later date.
The cornerstone of the cathedral was laid in 1263 by Friedrich and Konrad von Hochstaden. Construction lasted 281 years and was finally finished with the dedication of the Holy Spirit Chapel in 1544. The cathedral contains a five-aisle nave built in the Gothic style. In contrast to many other cathedrals of the period, St. Victor's lacks an ambulatory. Instead a twin pair of chapels is connected to the choir similar to that seen at the Church of Our Lady in Trier. Along with the monasterial library of the Cathedral houses one of the most important religious libraries of the Lower Rhine.
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.