The Byzantine empire

Around 300 A.D. began the decline of the Roman empire, and the Roman emeror Constantine moved his capital to Constantinople, now called Istanbul. It was here that he began establishing the Byzantine empire. Scholars came from all over Europe to study in Constantinople. Later, after the collapse of the remaining Roman empire, the Byzantine empire began to expand. 

Emperor Justinian-I regained most of the Roman empire and brought it under the Byzantine control. Christianity became the state religion and developing from constantinople, it spread into Europ. Art and trade flourished during this period even though the empire faced and warded off many attacks. Around 635 A.D. the Arabs began attacking the empire and by 640 A.D. they had captured most of the Middle East and African territories. With this began the downfall of the empire and it collapsed completely when constantinople fell to the Ottoman Turks in 1435.