Moscow ( or ; ) is the capital city and the most populous federal subject of Russia. The city is a major political, economic, cultural and scientific center in Russia and in Eastern Europe. According to Forbes 2013, Moscow has the largest number of billionaire residents in the world, has been ranked as the ninth most expensive city in the world by Mercer and is one of the world’s largest urban economies, being ranked as an alpha global city according to the Globalization and World Cities Research Network and is also one of the fastest growing tourist destinations in the world according to the MasterCard Global Destination Cities Index. Moscow is the northernmost and coldest megacity and metropolis on Earth, the most populous city in Europe, and the 8th largest city proper in the world, as well as the largest amongst high income economies. It is home to the Ostankino Tower, the tallest free standing structure in Europe; Mercury City Tower, the tallest skyscraper in Europe and the Moscow International Business Center. It is the largest city in Russia, with a population of 12,111,194 people (2014). By its territorial expansion on 1 July 2012 southwest into the Moscow Oblast, the capital increased its area 2.5 times; from about up to , and gained an additional population of 233,000 people. Moscow is situated on the Moskva River in the Central Federal District of European Russia making it the world’s most populated inland city. The city is well known for its unique architecture which consists of many different historic buildings such as Saint Basil’s Cathedral with its brightly colored domes. With over 40 percent of its territory covered by greenery, it is one of the greenest capitals and major cities in Europe and the world, having the largest forest in an urban area within its borders—more than any other major city—even before its expansion in 2012. In the course of its history the city has served as the capital of a progression of states, from the medieval Grand Duchy of Moscow and the subsequent Tsardom of Russia to the Soviet Union. Moscow is considered the center of Russian culture, having served as the home of prestigious Russian artists, scientists and sports figures during the course of its history and because of the presence of many different museums, academic and political institutions and theaters. Moscow is also the seat of power of the Government of Russia, being the site of the Moscow Kremlin, a medieval city-fortress that is today the residence of the Russian president. The Moscow Kremlin and the Red Square are also one of several World Heritage Sites in the city. Both chambers of the Russian parliament (the State Duma and the Federation Council) also sit in the city. The city is served by an extensive transit network, which includes four international airports, nine railway terminals, numerous trams, a monorail system and one of the deepest underground metro systems in the world, the Moscow Metro, the fourth-largest in the world and largest outside of Asia in terms of passenger numbers. It is recognized as one of the city’s landmarks due to the rich and varied architecture of its 194 stations. Over time, Moscow has acquired a number of epithets, most referring to its size and preeminent status within the nation: The Third Rome (), The Whitestone One (), The First Throne (), The Forty Forties (), and The Hero City (). In old Russian the word “” (forty) also meant a church administrative district, which consisted of about forty churches. The demonym for a Moscow resident is “” (moskvich), rendered in English as Muscovite.