Moscow is the capital and the most populous city and the most populous federal subject of Russia. Moscow is a major political, economic, cultural, religious, financial, educational, and transportation center of Russia and the world, a global city. It is also the seventh largest city proper in the world, a megacity. The population of Moscow (as of 1 September 2009) is 10,535,100. It is located by the Moskva River in the Central Federal District, in the European part of Russia. Moscow sits on the junction of three geological platforms. Historically, it was the capital of the former Soviet Union, Russian Empire, Tsardom of Russia and the Grand Duchy of Moscow. It is the site of the Moscow Kremlin, one of the World Heritage Sites in the city, which serves as the residence of the President of Russia. The Russian parliament (the State Duma and the Federation Council) and the Government of Russia also sit in Moscow. Moscow is a major economic centre. It is home to many scientific and educational institutions, as well as numerous sport facilities. It possesses a complex transport system that includes four international airports, nine railroad terminals, and the world`s second busiest (after Tokyo) metro system, which is famous for its architecture and artwork. Its metro is the busiest single-operator subway in the world.