Among the crowd of events witnessed under the dome of S. Sophia, there are three scenes of paramount importance in the religious history of the world that lend to the Great Church an extraordinary interest. The first occurred on the day on which the envoys of Vladimir attended service in the cathedral, and were so overwhelmed by the splendours of the worship, that they hastened back to Russia to tell their sovereign that they had seen the glory of the true God. “We know not,” they are reported to have said, “whether we were not in heaven; in truth, it would be impossible on earth to find such riches and magnificence. We cannot describe to you all that we have seen. We can only believe that there in all likelihood one is in the presence of God, and that the worship of other countries is there entirely eclipsed. We shall never forget such grandeur. Whosoever has seen so sweet a spectacle will be pleased with nothing elsewhere.” The conversion of the Slavic peoples to the Christian faith, a work commenced in the ninth century by the mission of Cyril and Methodius to the Slavs of Bulgaria and Moravia, is one of the most important services rendered by the Church of the Byzantine Empire to the cause of European civilisation. So far as its political significance is concerned, it can stand comparison with the conversion of the Teutons by the Western Church. It accomplished what the victories of Zimisces failed to achieve. It was the moral conquest of Russia, and the source of her upward life, until that country was opened also to the influence of Western civilisation. It probably saved Russia from becoming a Mohammedan State. The Slavic peoples rightly cherish a regard for Byzantine Constantinople, similar to that which Western Europe feels for Athens and Rome.