city, Moscow oblast (region), western Russia. It lies southeast of Moscow near the confluence of the Moskva and Oka rivers. First mentioned in 1177, Kolomna formed a key stronghold on Moscow's southern frontier; it was sacked four times by the Tatars. Kolomna was one of the earliest Russian locomotive-building centres, and today diesel engines, heavy machinery, and synthetic rubber are produced. Pop. (2006 est.) 148,020.