The term CITY ON THE IRTYSH is solved by the four letter word OMSK. Omsk is a city located in southwestern Siberia, Russia, on the banks of the Irtysh River. It is the administrative center of Omsk Oblast and one of the largest cities in Russia. Omsk was founded in 1716 as a fortress to protect the expanding Russian Empire from Mongol raids. Today, it is an important industrial, cultural, and educational center in Russia.