 In 1821, as part of the Mikhail Speransky's reforms, Siberia was administratively divided at the Yenisei River.Irkutsk became the seat of the Governor-General of East Siberia.In the early 19th century, many Russian artists, officers, and nobles were sent into exile in Siberia for their part in the Decembrist revolt against Tsar Nicholas I. Irkutsk became the major center of intellectual and social life for these exiles, and they developed much of the city's cultural heritage.