Oka River in the context of Kolomna

The Oka–Don Lowlands (Russian: Окско-Донская равнина) (also: Oka–Don Plain), is a flat plain in European Russia, bounded on the north by the Oka River (and the Meshchera Lowlands), on the south by the Don River, on the west by the Central Russian Upland, and on the east by the Volga Upland. The area is part of the larger East European Plain. The terrain is flat, with altitude averaging 160 meters above sea level, and the rivers meander on broad floodplains. Agricultural use of the plain is high, mostly for grain growing – wheat, barley and rye. The plain provides a flat south–north route for transportation, situated between uplands. Until a line of forts was built across the territory by the Russian government in the 1640s (the Belgorod Line), the plain was a route for Tatar invasion from the south.

The Don (Russian: Дон, romanized: don) is the fifth-longest river in Europe. Flowing from Central Russia to the Sea of Azov in Southern Russia, it is one of Russia's largest rivers and played an important role for traders from the Byzantine Empire.

Its basin is between the Dnieper basin to the west, the lower Volga basin immediately to the east, and the Oka basin (tributary of the Volga) to the north. Native to much of the basin were Slavic nomads.

Russia can be divided into an European and an Asian part. The dividing line is generally considered to be the Ural Mountains. The European part is drained into the Arctic Ocean, Baltic Sea, Black Sea, and Caspian Sea. The Asian part is drained into the Arctic Ocean and the Pacific Ocean.

Notable rivers of Russia in Europe are the Volga (which is the longest river in Europe), Pechora, Don, Kama, Oka and the Northern Dvina, while several other rivers originate in Russia but flow into other countries, such as the Dnieper (flowing through Russia, then Belarus and Ukraine and into the Black Sea) and the Western Dvina (flowing through Russia, then Belarus and Latvia into the Baltic Sea).

The Don (Russian: Дон) is the fifth-longest river in Europe. Flowing from Central Russia to the Sea of Azov in Southern Russia, it is one of Russia's largest rivers and played an important role for traders from the Byzantine Empire.

Its basin is between the Dnieper basin to the west, the lower Volga basin immediately to the east, and the Oka basin (tributary of the Volga) to the north. Native to much of the basin were Slavic nomads.

Kaluga (Russian: Калу́га, IPA: [kɐˈɫuɡə] ) is a city and the administrative center of Kaluga Oblast, Russia. It stands on the Oka River 150 kilometers (93 mi) southwest of Moscow. Its population was 337,058 at the 2021 census.

Kaluga's most famous resident, the space travel pioneer Konstantin Tsiolkovsky, worked there as a school teacher from 1892 to 1935. The Tsiolkovsky State Museum of the History of Cosmonautics in Kaluga is dedicated to his theoretical achievements and to their practical implementations for modern space research, hence the motto on the city's coat of arms: Колыбель Космонавтики, Kolybélʹ kosmonávtiki ("The Cradle of Space-Exploration").

The Voronezh (Russian: Воро́неж, pronounced [vɐˈronʲiʂ]), also romanized as Voronež, is a river in Tambov, Lipetsk, and Voronezh oblasts in Russia, a left tributary of the Don. The Voronezh is 342 kilometres (213 mi) long, with a drainage basin of 21,600 square kilometres (8,300 sq mi). It freezes up in the first half of December and stays under the ice until late March. The lower reaches of the river are navigable. The cities of Lipetsk and Voronezh are along the Voronezh River.

Going upstream, it leaves the Don south of Voronezh and goes north parallel and east of the Don for about 150 kilometres (93 mi). West of Michurinsk it swings east and splits into the Lesnoy and Polny Voronezh Rivers ("Forest and Field Voronezh"). These go north about 75 kilometres (47 mi) to the border of Ryazan Oblast. To the north are tributaries of the Oka. To the east are the basins of the south-flowing Bityug which joins the Don and the north-flowing Tsna which reaches the Oka via the Moksha.

The Meshchera or Meshchyora (Russian: Мещёра) were a Finno-Ugric tribe in the Volga region between the Oka River and the Klyazma river, today called the Meshchera Lowlands, who assimilated with the neighbouring tribes around the 16th century.

Ryazan (Russian: Рязань, IPA: [rʲɪˈzanʲ] ; also Riazan) is the largest city and administrative center of Ryazan Oblast, Russia. The city is located on the banks of the Oka River in Central Russia, 196 km (122 mi) southeast of Moscow. As of the 2010 Census, Ryazan had a population of 524,927, making it the 33rd most populated city in Russia, and the fourth most populated in Central Russia after Moscow, Voronezh, and Yaroslavl.

An older city, now known as Old Ryazan (Russian: Старая Рязань, romanized: Staraya Ryazan), was located 50 kilometres (31 mi) east of modern-day Ryazan during the late Middle Ages, and served as capital of the Principality of Ryazan up until the Mongol invasion in 1237. During the Siege of Ryazan, it became one of the first cities in Russia to be besieged and completely razed to the ground. The capital was subsequently moved to Pereyaslavl-Ryazansky (Russian: Переяславль-Рязанский), and later renamed to Ryazan by order of Catherine the Great in 1778.

Murom (Russian: Муром, IPA: [ˈmurəm]) is a historical city in Vladimir Oblast, Russia, which sprawls along the west bank of the Oka River. It borders Nizhny Novgorod Oblast and is situated 137 kilometres (85 mi) from the administrative center Vladimir. Its population as of the 2021 Census was 107,497.

Dzerzhinsk (Russian: Дзержи́нск, IPA: [dzʲɪrˈʐɨnsk]) is a city in Nizhny Novgorod Oblast, Russia, located along the Oka River, about 370 kilometers (230 mi) east of Moscow and 35 kilometers (22 mi) west of Nizhny Novgorod. Population: 240,742 (2010 census); 261,334 (2002 census); 285,071 (1989 Soviet census).

It was previously known as Rastyapino (until 1929).

Arzamas (Russian: Арзама́с, IPA: [ɐrzɐˈmas] ) is a city in Nizhny Novgorod Oblast, Russia, located on the Tyosha River (a tributary of the Oka), 410 kilometers (250 mi) east of Moscow. As of 2024, it has a population of 103,629.