Moscow ) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 12.4 million residents within the city limits, while over 17 million residents in the urban area, and over 20 million residents in the Moscow Metropolitan Area. The city covers an area of 2,511 square kilometres , while the urban area covers 5,891 square kilometres , and the metropolitan area covers over 26,000 square kilometres . Moscow is among the world's largest cities, being the most populous city entirely within Europe, the most populous urban area in Europe, the most populous metropolitan area in Europe, and also the largest city by land area on the European continent.Originally established in 1147 as a minor town, Moscow grew to become a prosperous and powerful city that served as the capital of the Grand Duchy that bears its namesake. When the Grand Duchy of Moscow evolved into the Tsardom of Russia, Moscow still remained as the political and economic center for most of the Tsardom's history. When the Tsardom was reformed into the Russian Empire, the capital was moved from Moscow to Saint Petersburg, diminishing the influence of the city. The capital was then moved back to Moscow following the Russian Revolution and the city was brought back as the political centre of the Russian SFSR and the Soviet Union. When the Soviet Union dissolved, Moscow remained as the capital city of the contemporary and newly established Russian Federation. As the northernmost and coldest megacity in the world, and with a history that dates over eight centuries, Moscow is governed as a federal city that serves as the political, economic, cultural, and scientific centre of Russia and Eastern Europe. As an alpha world city, Moscow has one of the world's largest urban economies, and is one of the most expensive cities in the world, and is also one of the fastest growing tourist destinations in the world. Moscow is home to the third-highest number of billionaires of any city in the world, and has the highest number of billionaires of any city in Europe. The Moscow International Business Center is one of largest financial centres of Europe and the world, and features some of Europe's tallest skyscrapers. Moscow is also home to the tallest free-standing structure in Europe, the Ostankino Tower, and was the host city of the 1980 Summer Olympics, and one of the host cities of the 2018 FIFA World Cup. As the cultural centre of Russia, Moscow served as the home of Russian artists, scientists, and sports figures due to the presence of its numerous museums, academic and political institutions and theatres. The city is home to several UNESCO World Heritage Sites, and is well known for its display of Russian architecture, particularly its historic buildings such as the Saint Basil's Cathedral, the Red Square, and the Moscow Kremlin, of which the latter serves as the seat of power of the Government of Russia. Moscow is home to many Russian companies in numerous industries, such as finance and technology. Moscow is served by a comprehensive transit network, which includes four international airports, nine railway terminals, a tram system, a monorail system, and most notably the Moscow Metro, the busiest metro system in Europe, and one of the largest rapid transit systems in the world. With over 40 percent of its territory covered by greenery, it is one of the greenest cities in Europe and the world.