Russia, or the Russian Federation, is a transcontinental country located in Eastern Europe and Northern Asia. Covering an area of 17,125,200 square kilometres , it is the largest country in the world by area, spanning more than one-eighth of the Earth's inhabited land area, stretching eleven time zones, and bordering 16 sovereign nations. The territory of Russia extends from the Baltic Sea in the west to the Pacific Ocean in the east, and from the Arctic Ocean in the north to the Black Sea and the Caucasus in the south. With 146.7 million inhabitants living in the country's 85 federal subjects, Russia is the most populous nation in Europe and the ninth-most populous nation in the world. Russia's capital and largest city is Moscow; other major urban areas include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod, Kazan, Chelyabinsk and Samara. The East Slavs emerged as a recognisable group in Europe between the 3rd and 8th centuries AD. The medieval state of Rus' arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' ultimately disintegrated into a number of smaller states, until it was finally reunified by the Grand Duchy of Moscow in the 15th century. By the 18th century, the nation had greatly expanded through conquest, annexation, and exploration to become the Russian Empire, which became a major European power, and the third-largest empire in history, stretching from Norway on the west to Canada on the east. Following the Russian Revolution, the Russian SFSR became the largest and leading constituent of the Soviet Union, the world's first constitutionally socialist state. The Soviet Union played a decisive role in the Allied victory in World War II, and emerged as a recognised superpower and rival to the United States during the Cold War. The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. Following the dissolution of the Soviet Union in 1991, the Russian SFSR reconstituted itself as the Russian Federation and is recognised as the continuing legal personality and a successor of the USSR.Following the constitutional crisis of 1993, a new constitution was adopted and Russia has been governed as a federal semi-presidential republic. Vladimir Putin became acting president on 31 December 1999 after Russia's first president, Boris Yeltsin, resigned and he was elected president in March 2000. Since then, he has dominated Russia's political system as either president or prime minister. His government has been accused by non-governmental organisations of human rights abuses, authoritarianism and corruption. The Russian economy ranks as the fifth-largest in Europe, the eleventh-largest in the world by nominal GDP and the fifth-largest by PPP. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally. The country is one of the five recognised nuclear weapons states and possesses the largest stockpile of nuclear warheads. Russia is a major great power, as well as a regional power, and has been characterised as a potential superpower. The Russian Armed Forces have been ranked as the world's second most powerful, and the most powerful in Europe. Russia hosts the world's ninth-greatest number of UNESCO World Heritage Sites, at 29, and is among the world's most popular tourist destinations. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation , the G20, the Council of Europe, the Asia-Pacific Economic Cooperation , the Organization for Security and Co-operation in Europe , the International Investment Bank and the World Trade Organization , as well as being the leading member of the Commonwealth of Independent States , the Collective Security Treaty Organization and a member of the Eurasian Economic Union .