First definitions:

Byzantine |ˈbizənˌtēn; bəˈzan-; -ˌtīn|
adjective

of or relating to Byzantium, the Byzantine Empire, or the Eastern Orthodox Church.

• of an ornate artistic and architectural style that developed in the Byzantine Empire and spread esp. to Italy and Russia. The art is generally rich and stylized (as in religious icons) and the architecture typified by many-domed, highly decorated churches.