The Oka River flows through the European part of Russia, starting in the Central Russian Upland and joining the Volga River in Nizhny Novgorod. The Oka River basin covers an area of about 245,000 square kilometers (95,000 sq mi) and includes parts of the Moscow, Kaluga, Tula, Ryazan, Vladimir, and Nizhny Novgorod regions. The Oka River is navigable for much of its length and has been an important trade route for centuries.
The city of Kaluga is located on the left bank of the Oka River, about 180 kilometers (112 miles) southwest of Moscow. Kaluga is the administrative center of Kaluga Oblast and has a population of about 330,000 people. Kaluga is a major industrial and cultural center and is home to a number of universities and colleges.
