The Church of Christ Pantocrator is a medieval Eastern Orthodox church in Nesebar, on the Black Sea coast. It is usually dated to the late 13th or early 14th century. The church, today an art gallery, survives largely intact and is among Bulgaria's best preserved churches of the Middle Ages.
The best-known feature of the Church of Christ Pantocrator is the rich and colourful decoration of its exterior walls. The most lavishly decorated part of the church is the east side with the apse, and as a whole all sides of the church exhibit different ornamentation. Interchanging strips of three or four rows of bricks and carved stones, which create an optical pattern, are the most basic type of decoration used.
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.