City of Omsk and Omsk region Omsk is one of the largest cities in Russia, located at the confluence of the Irtysh and Om rivers. City-millionaire - 1,154,507 people. (2020). Second largest in Siberia and ninth in Russia A major transport hub: the Trans-Siberian railway passes through the city from west to east, and the navigable Irtysh River from south to north Founded in 1716. Officially re...