Moscow’s architectural and performing arts culture are world-renowned. Moscow is also well known as the site of the Saint Basil's Cathedral, with its elegant onion domes, as well as the Cathedral of Christ the Savior. The Patriarch of Moscow, whose residence is the Danilov Monastery, serves as the head of the Russian Orthodox Church. The Moscow Kremlin is a historic fortified complex, overlooking the Moskva River, Red Square and the Alexander Garden.  It is the best known of kremlins (citadels) and includes four palaces, four cathedrals, and the enclosing Kremlin Wall with Kremlin towers. Moscow also remains a major economic center and is perennially considered one of the most expensive cities in the world. It is home to many scientific and educational institutions, as well as numerous sport facilities. Many of Moscow's museums and galleries have collections that can be compared to those of the best museums of the West. Western Europe and North America. Frequent art exhibitions thrive on both the new and the classic, as they once did in pre-Revolutionary times, and are derived from diverse branches of the arts - painting, photography, and sculpture. Moscow is also the heart of Russian performing arts, including ballet and film. There are ninety-three theaters, 132 cinemas and twenty-four concert-halls in Moscow. Among Moscow's many theatres and ballet studios is the famous Bolshoi Theatre. There are 96 parks and 18 gardens in Moscow, including 4 botanical gardens.