Saint Sophia cathedral in Kyiv is the UNESCO World Heritage Site, just one Orthodox place in the world there so many mosaics and frescos. Saint Sophia cathedral was built in the early 11th century by the great prince of Kievan Rus Yaroslav the Wise. His wife Ingegerd Olofsdotter was a Swedish princess who adopted Eastern Christianity. Their daughter Anna became the queen of France. In honor of his wife Yaroslav built the cathedral of Saint Irene nearby the Golden Gate. Unfortunately this church was destroyed by the Bolsheviks.
Reconstruction of Yaroslav and Ingegerd wedding you can see here.