From Wikipedia; please see the article if you're interested in further information.

The Steppes
The steppe has long been depicted as the typical Russian landscape. It is a broad band of treeless, grassy plains, interrupted by mountain ranges, extending from Hungary across Ukraine, southern Russia, and Kazakhstan before ending in Manchuria. Most of the Soviet Union's steppe zone was located in the Ukrainian and Kazakh republics; the much smaller Russian steppe is located mainly between those nations, extending southward between the Black and Caspian Seas before blending into the increasingly desiccated territory of the Republic of Kalmykia. In a country of extremes, the steppe zone provides the most favorable conditions for human settlement and agriculture because of its moderate temperatures and normally adequate levels of sunshine and moisture. Even here, however, agricultural yields are sometimes adversely affected by unpredictable levels of precipitation and occasional catastrophic droughts. The soil is very dry.

The Eurasian Steppe (sometimes referred to collectively as The Steppes or The Steppe) is the term often used to describe the vast steppe ecoregion of Eurasia stretching from the western borders of the steppes of Hungary to the eastern border of the steppes of Mongolia, for roughly 5000 km. Most of the Euro-Asian Steppe is included within the region of Central Asia while only a small part of it is included within Eastern Europe. The term Asian Steppe usually describes the Euro-Asian Steppe without its most western parts, i.e., the steppes of western Russia, Ukraine and Hungary.

The Pontic steppe covers an area of 994,000 square kilometres (384,000 sq mi), extending from eastern Romania across southern Moldova, Ukraine, Russia and northwestern Kazakhstan to the Ural Mountains. The Pontic steppe is bounded by the East European forest steppe to the north, a transitional zone of mixed grasslands and temperate broadleaf and mixed forests. To the south, the Pontic steppe extends to the Black Sea, excepting the Crimean and western Caucasus mountains' border with the sea, where the Crimean Submediterranean forest complex defines the southern edge of the steppes. The steppe extends to the western shore of the Caspian Sea in the Dagestan region of Russia, but the drier Caspian lowland desert lies between the Pontic steppe and the northwestern and northern shores of the Caspian. The Kazakh Steppe bounds the Pontic steppe on the southeast.

The Ponto-Caspian seas are the remains of the Turgai Sea, an extension of the Paratethys which extended south and east of the Urals and covering much of today's West Siberian Plain in the Mesozoic and Cenozoic.