The Byzantine Empire

After the division of the Eastern and Western parts of Rome, the eastern remained under the rule of Constantine, the first Christian emperor of Rome. Constantine moved the capital from Rome to the city of Byzantium. He rebuilt the city and called it Constantinople, naming it after himself. This new capital city represents the end of the Roman Empire and the beginning of the Byzantine Empire. He began building monuments to create a more Christian feel in the new capital city. The first church built there by Constantinople was the church of St Eirene, and it was dedicated to Holy peace.
The fall of Rome ended the western half of the Roman Empire, and the eastern half continued as the Byzantine Empire. The empire had many different elements, a few of which were Christianity and Greek education. The Christianity developed here was the most significant cultural feature of the Byzantium Empire. It had a major influence on Orthodox Christianity, and missionary work began its spread.
The Byzantine Empire covered Greece, Balkans, Asia Minor, Syria, and Egypt. The empire looked less like a Roman empire, and had more of a Greek aspect, because the Greeks were the predominant race in the empire. Greek became the main language of the empire, replacing Latin. Also, legislation became thoroughly Greek.
The Byzantine Empire fell to Muslim invaders in 1453 because of the sack of Constantinople.
The Christianity and Greek influence in the Byzantine empire was extremely important. The spread of Orthodox Christianity lead to the adoption of a new religion still practiced in many places today. Without Constantine, and the Byzantine empire, Christianity might not have spread the way it did, and the religion would not be how it is today.

http://www.gothicmed.com/gothicmed/GothicMed/virtual-museum/greece/General/Byzantio.html
http://www.fordham.edu/halsall/byzantium/index.html
http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ac59
http://www.lycos.com/info/byzantine-empire.html

Byzantium and the History of the Orthodox Church

Byzantium was an ancient Roman city that served as a major hub for Christianity. In contrast with today’s untheological mindset, Byzantium flourished with religious festivities and passionately heated debates. It was a powerful center for Christian civilization, with which any other Roman or European city could not compete.

There was no clear line that divided the church from the state in Byzantium. The two were seen as one unit, not truly separable. Emperors Constantine and Justinian played significant roles in blurring this division. The emperor played an important role in several religious ceremonies, as he was viewed as a symbol of the monarchy of God in Heaven.

Monasticism was a large aspect of religious life in Byzantium. It started in Egypt and Syria but quickly found its way into Christendom. There are three different aspects of monasticism: “first the hermits, ascetics leading the solitary life in huts or caves, and even in tombs, among the branches of trees, or on the tops of pillars … Secondly there is the community life, where monks dwell together under a common rule and in a regularly constituted monastery … Finally there is a form of the monastic life intermediate between the first two, the semi-eremitic life, a 'middle way' where instead of a single highly organized community there is a loosely knit group of small settlements, each settlement containing perhaps between two and six members living together under the guidance of an elder.”

It is interesting to read about the history of a religion that is so popular today. There are several aspects to the religion that are not commonly known, even though so many know the generalities about such a religion.

Reference:
http://www.orthodoxinfo.com/general/history3.aspx#Byzantine%20Christianity