 With a population of 617,473 as of the 2010 Census, Irkutsk is the 25th largest city in Russia by population, the 5th largest in the Siberian Federal District, and one of the largest cities in Siberia.Located in the south of the eponymous oblast, the city proper lies on the Angara River, a tributary of the Yenisei, about 850 kilometres (530 mi) to the south-east of Krasnoyarsk and about 520 kilometres (320 mi) north of Ulaanbaatar.The Trans-Siberian Highway (Federal M53 and M55 Highways) and Trans-Siberian Railway connect Irkutsk to other regions in Russia and Mongolia.