Moscow is the capital of Russia and the country's economic, financial, educational, and transportation center. It is located on the Moskva River in the Central Federal District, in the European part of Russia. Moscow is the most populous city in Europe, with a population of 13.7 million. Historically, it was the capital of the former Soviet Union and the Grand Duchy of Moscow, the pre-Imperial Russian state. It is the site of the Kremlin, which now serves as the ceremonial residence of the President of Russia. Moscow's architecture and performing arts culture are 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 Russian Orthodox Church. Moscow also remains a major economic centre and is home to a large number of billionaires; it is perennially considered one of the most expensive cities for expatriate employees in the world. It is home to many scientific and educational institutions, as well as numerous sport facilities. It possesses a complex transport system that includes the world's busiest metro system, which is famous for its architecture.
