Mainz, known as Mogontiacum, was Rome’s most important city in Germania. In fact, the stage and auditorium of the Mainz theater was the largest anywhere north of the Alps. More than 10,000 audience members could be accommodated. The theater proportions were gigantic: The stage measured 42 meters wide. The audience area was 116 meters in width. The Roman Theater is located just above the Mainz-South Station adjacent the the “Roemisches Theater”-Station.
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.