One of the world's greatest cities, Moscow (Moskva) is the capital of Russia. Since it was first mentioned in chronicles of 1147, Moscow has played a vital role in Russian history; indeed, the history of the city and of the Russian nation are closely interlinked. Today Moscow is not only the political centre of Russia but also the country's leading city in population, in industrial output, and in cultural, scientific, and educational importance. For more than 600 years Moscow has been the spiritual centre of the Russian Orthodox Church. The capital of the Union of Soviet Socialist Republics (the U.S.S.R.) until its dissolution in 1991, Moscow attracted world attention as a centre of Communist power; the name of the seat of the former Soviet government and successor Russian government, the Kremlin (Russian Kreml), became a synonym for Soviet authority. The dissolution of the U.S.S.R. brought economic and political change, along with a degree of uncertainty over the future, to the city. Moscow covers an area of about 386 square miles (1,000 square kilometres), its outer limit being roughly delineated by the Moscow Ring Road. Most of the area beyond this highway has been designated as a Forest-Park Zone, or greenbelt.