Moscow became the capital of Russia and the Soviet Union after the revolution of 1917. Then it had 1.7 million inhabitants. Today the city has more than 9 million inhabitants and about 1000 km2 (40 km from one side to the other). In 1932 construction of Moscow's metro began as a piece of art with elegant and huge stations. Today the Moscow metro seems to be the busiest in the world, carrying an average of 8-9 million passengers on a normal weekday, i.e. some 3,000,000,000 a year.
