The Byzantine movement began in Constantinople the new Rome located in the greek city Byzantium . During the Bezantine era christianity spread quickly. Christianity became established as the official state religion in 391 C.E. a ban again pagan worship was set in place . The Justinian empire marks the beginning of this era. Justinian is responsible for the construction and reconstruction of over 30 churches in Constantinopole . Monument constructed by Justinian such Hagia Sophia defined Byzantine architecture forever.