Mosynopolis , of which only ruins now remain in Greek Thrace, was a city in the Roman province of Rhodope, which was known until the 9th century as Maximianopolis. The city of Maximianopolis appears in written sources from the 4th century on. Its fortifications were renewed by Byzantine emperor Justinian I, and it was later a base for operations by Emperor Basil II in his wars against the Bulgarians.
In the 11th century, the city was the center of a district (bandon) in the theme of Boleron, and Anna Komnene reports in her Alexiad that there were many Manichaeans living in Mosynopolis in the late 11th/early 12th centuries. The town was captured in 1185 by the Normans, while the monk Ephrem says that the city was captured in 1190 by Frederick I, Holy Roman Emperor. The Battle of Messinopolis, in which the Bulgarians defeated Boniface I, Marquess of Montferrat, took place nearby in 1207, and was speedily followed by the destruction of Mosynopolis by Tsar Kaloyan of Bulgaria.
Bishops of Maximianopolis in Rhodope were present at the 5th and 6th-century ecumenical councils of Ephesus (431), Chalcedon (451), and Constantinople II (553) and in another council of 459. From the 7th to the 9th centuries, the see is referred to as archiepiscopal, giving it autocephalous status.
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.