Doclea (also Dioclea) was a Roman city, the seat of the Late Roman province of Praevalitana, and an Archbishopric, which is now a Latin Catholic titular see.
The Romanized Illyrian tribe known as Docleatae that inhabited the area derived their name from the city. It was the largest settlement of the Docleatae, founded in the first decade of the 1st century AD. Doclea was built to conform to the terrain. It was a large town with 8–10,000 inhabitants. The surrounding area had a relatively high population density within a radius of 10 km due to the city's geographical position, a favorable climate, positive economic conditions and defensive site that were of great importance at that time.
After the administrative division of the Roman Empire in 297, Doclea became the capital of the newly established Roman province of Praevalitana.
In the 4th and the 5th centuries, it was taken by the barbarian tribes and went into decline. At the beginning of the 5th century, it was attacked by the Germanic Visigoths. A severe earthquake destroyed it in 518. The South Slavs proceeded to rebuild the settlement in the 7th century. The historical ruins of the town can be seen today.
Circa 400, the city became the seat of an archdiocese, apparently Metropolitan as capital of a Late Roman province Dalmatia Superior. It was suppressed in 927. From 1034 till circa 1100, it was nominally united (as a title) with the then still Metropolitan Archdiocese of Bar (Antivari), also in modern Montenegro.
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.