The medieval state of Kievan Rus' incorporated parts of what is now modern Ukraine, Russia, and Belarus, and was centered on Kiev and Novgorod. Its architectural style quickly established itself after the adoption of Christianity in 988 and was strongly influenced by the Byzantine. After the disintegration of Kievan Rus' followed by Mongol invasion in the first half of the 13th century, the architectural tradition continued in the principalities of Novgorod, Vladimir-Suzdal, Galicia-Volhynia and eventually had direct influence on the Russian, Ukrainian, and Belarusian Architecture.