Kiev, also spelled Kyiv (Ukrainian: Київ , Kyyiv, IPA: [ˈkɨjiʋ]; Russian: Ки́ев , Kiyev; see also Cities' alternative names), is the capital and the largest city of Ukraine, located in the north central part of the country on the Dnieper river. Kiev is an important industrial, scientific, educational and cultural centre of Eastern Europe. It is home to many high-tech industries, higher education institutions and world-famous historical landmarks. The city has an extensive infrastructure and highly developed system of public transport, including the Kiev Metro. The name Kiev is said to derive from the name of Kyi, one of four legendary founders of the city (brothers Kyi, Shchek, Khoryv and sister Lybid'). During its history, Kiev, one of the oldest cities in Eastern Europe, passed through several stages of great prominence and relative obscurity. The city is believed to have been founded in the 5th century as a trading post in the land of Early East Slavs. It gradually acquired eminence as the centre of the East Slavic civilization, becoming in the tenth to twelfth centuries a political and cultural capital of Rus', a medieval East Slavic state. Completely destroyed during the Mongol invasion in 1240, the city lost most of its influence for the centuries to come. It was a provincial capital of marginal importance in the outskirts of the territories controlled by its powerful neighbors: first the Grand Duchy of Lithuania, followed by Poland and Russia. The city prospered again during the Russian industrial revolution in the late 19th century. After the turbulent period following the Russian Revolution of 1917, from 1921 onwards Kiev was an important city of the Ukrainian Soviet Socialist Republic, and, since 1934, its capital. During World War II, the city again suffered significant damage, but quickly recovered in the post-war years remaining the third largest city of USSR. Following the collapse of the Soviet Union and the Ukrainian independence of 1991, Kiev remained the capital of Ukraine.