It is also the largest city in Europe, with the Moscow metropolitan area ranking among the largest urban areas in the world. Moscow is the country's political, economic, religious, financial, educational and transportation centre. It is located on the Moskva River in the Central Federal District, in the European part of Russia. Historically, it was the capital of the former Soviet Union and the Grand Duchy of Moscow and Tsardom of Russia, the pre-Imperial Russian states.
It is the site of the Moscow Kremlin, which serves as the ceremonial residence of the President of Russia. Moscow is a major economic centre and is home to the largest number of billionaires in the world; in 2007 Moscow was named the world's most expensive city for foreign employees for the second year in a row. It is home to many scientific and educational institutions, as well as numerous sport facilities. It possesses a complex transport system, that includes one of the world's busiest metro systems which is famous for its architecture and artwork.
Moscow is situated on the banks of the Moskva River, which flows for just over 500 km through the East European Plain in central Russia. 49 bridges span the river and its canals within the city's limits.
Moscow's road system is centered roughly around the Kremlin at the heart of the city. From there, roads generally radiate outwards to intersect with a sequence of circular roads ("rings").
Moscow's architecture is world-renowned. Moscow is also well known as the site of Saint Basil's Cathedral, with its elegant onion domes, as well as the Cathedral of Christ the Savior and the Seven Sisters. The Patriarch of Moscow, whose residence is the Danilov Monastery, serves as the head of the Orthodox Church. Moscow also hosted the 1980 Summer Olympics.