The Russian Orthodox Church, alternatively legally known as the Moscow Patriarchate, is an autocephalous Eastern Orthodox Christian church. It has 194 dioceses inside Russia. The primate of the ROC is the Patriarch of Moscow and all Rus'.
Cathedral of Christ the Saviour in Moscow, Russia
Russian Orthodox monks defended the Trinity monastery against Polish troops during the Time of Troubles. Painting by Sergey Miloradovich.
An Old Believer Priest, Nikita Pustosviat, Disputing the Matters of Faith with Patriarch Joachim. Painting by Vasily Perov
St. Sophia-Assumption Cathedral in Tobolsk
Russian is an East Slavic language, spoken primarily in Russia. It is the native language of the Russians and belongs to the Indo-European language family. It is one of four living East Slavic languages, and is also a part of the larger Balto-Slavic languages. It was the de facto and de jure official language of the former Soviet Union. Russian has remained an official language in independent Russia, Belarus, Kazakhstan, Kyrgyzstan, and Tajikistan, and is still commonly used as a lingua franca in Ukraine, Moldova, the Caucasus, Central Asia, and to a lesser extent in the Baltic states and Israel.
This page from an "ABC" book printed in Moscow in 1694 shows the letter П.
The Ostromir Gospels of 1056 is the second oldest East Slavic book known, one of many medieval illuminated manuscripts preserved in the Russian National Library.