History of the Russian Orthodox Church
The history of the Russian Orthodox Church begins with the Christianization of Kievan Rus' in 988 during the reign of Vladimir the Great. In the following centuries, Kiev and later other cities, including Novgorod, Pskov, Rostov, Suzdal and Vladimir, became important regional centers of Christian spirituality and culture.
Source: Wikipedia — History of the Russian Orthodox Church (CC BY-SA 4.0)