The most significant event of the Second Millennium

Justinian555AD the Empire

Christ_Pantocrator_coin-Solidus depicting Christ Pantocrator, a common motif on Byzantine coins. of Byzantine Empire

The Byzantine Empire, also referred to as the Eastern Roman Empire, or Byzantium, was the continuation of the Roman Empire in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern Istanbul, formerly Byzantium). It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Empire in 1453

"Saints Cyril and Methodius holding the Cyrillic alphabet," a mural by Bulgarian iconographer Z. Zograf, 1848, Troyan Monastery

https://en.wikipedia.org/wiki/Byzantine_Empire