Tula is the largest city and the administrative center of Tula Oblast in Russia, located 193 kilometers south of Moscow. Tula is located in the northern Central Russian Upland on the banks of the Upa River, a tributary of the Oka. At the 2010 census, Tula had a population of 501,169, an increase from 481,216 in 2002, making it the 32nd-largest city in Russia by population. A primarily industrial city, Tula was a fortress at the border of the Principality of Ryazan.