Byzantium. The history of the disappeared empire

Having arisen on the wreckage of the Great Roman Empire, Byzantium throughout its more than thousand -year history was an arena of constant invasions, siege and wars. The border of the West and the East, the symbol of the Christian world - Constantinople - beckoned the invaders, striking with his wealth and splendor.
How did the Byzantine Empire, which once belonged to half the world, despite all the shocks, existed amazingly long and why did it disappear almost without a trace, as if dissolved? Neither the powerful army, nor the skill of its politicians, nor the impregnable walls of Constantinople, nor the belief that God will not leave the first Christian empire, which spread the new religion, not only in its vast territory, but also in neighboring states, saved the ancient power.
About how it originated, the Rules of the world and the Byzantium died, as well as what heritage left the modern world, says British historian Jonathan Harris.
In the middle of the 16th century, the capital of the Ottoman Sultanate was one of the largest and richest cities in the world. It was the heart of the empire spreading from Crimea to Algeria, and its rapidly growing population was more than 400,000. Widely known as Istanbul, officially the city was called Constantinople