Kazakhstan, also Kazakstan (Kazakh: Қазақстан, Qazaqstan, IPA: [qɑzɑqˈstɑn]; Russian: Казахстан, Kazakhstán, Russian pronunciation: [kazəxˈstan]), officially the Republic of Kazakhstan, is a country in Central Asia and Europe. Ranked as the ninth largest country in the world as well as the world's largest landlocked country, it has a territory of 2,727,300 km² (greater than Western Europe). It is bordered by Russia, Kyrgyzstan, Turkmenistan, Uzbekistan and China. The country also borders on a significant part of the Caspian Sea. Vast in size, the land in Kazakhstan is very diverse in types of terrain: flatlands, steppes, taigas, rock-canyons, hills, deltas, mountains, snow-capped mountains, and deserts. Kazakhstan has the 62nd largest population in the world, with a population density of less than 6 people per square kilometre (15 per sq. mi.). For most of its history the territory of modern-day Kazakhstan has been inhabited by nomadic tribes. By the 16th century the Kazakhs emerged as a distinct group, divided into three hordes. The Russians began advancing into the Kazakh steppe in the 18th century, and by the mid-19th century all of Kazakhstan was part of the Russian Empire. Following the 1917 Russian Revolution, and subsequent civil war, the territory of Kazakhstan was reorganized several times before becoming the Kazakh Soviet Socialist Republic in 1936, a part of the USSR. During the 20th century, Kazakhstan was the site of major Soviet projects, including Khrushchev's Virgin Lands campaign, the Baikonur Cosmodrome, and the Semipalatinsk "Polygon", the USSR's primary nuclear weapon testing site. With an area of 2.7 million square kilometers (1.05 million sq. mi), Kazakhstan is the ninth-largest country in the world and the largest landlocked country in the world. It is equivalent to the size of Western Europe. It shares borders of 6,846 kilometers (4,254 mi) with Russia, 2,203 kilometers (1,369 mi) with Uzbekistan, 1,533 kilometers (953 mi) with China, 1,051 kilometers (653 mi) with Kyrgyzstan, and 379 kilometers (235 mi) with Turkmenistan. Major cities include Astana, Almaty, Karagandy, Shymkent, Atyrau and Oskemen. While located primarily in Asia, a small portion of Kazakhstan is also located west of the Urals in Eastern Europe.