These include initial roots which were established in the Eastern Slavic state of Kievan Rus'. Since the Christianization of Kievan Rus' for several ages Ukrainian architecture was influenced by the Byzantine architecture. After the 12th century, the distinct architectural history continued in the principalities of Galicia-Volhynia. During the epoch of the Zaporozhian Cossacks, a new style unique to Ukraine was developed under the western influences of the Polish–Lithuanian Commonwealth. After the union with the Tsardom of Russia, many structures in the larger eastern, Russian-ruled area were built in the styles of Russian architecture of that period, whilst the western Galicia was developed under Austro-Hungarian architectural influences. Ukrainian national motifs would finally be used during the period of the Soviet Union and in modern independent Ukraine.