Saint Petersburg ), formerly known as Petrograd , then Leningrad , is a city on the Neva River, at the head of the Gulf of Finland on the Baltic Sea. It is Russia's second-largest city after Moscow. With a population of roughly 5.4 million inhabitants, it is the fourth-most populous city in Europe, the most-populous city on the Baltic Sea, as well as the northernmost metropolis in Europe and the world. As an important Russian port on the Baltic Sea, it is governed as a federal city. The city was founded by Tsar Peter the Great on 27 May 1703 on the site of a captured Swedish fortress, and was named after apostle Saint Peter. Saint Petersburg is historically and culturally associated with the birth of the Russian Empire and Russia's entry into modern history as a European great power. It served as a capital of the Tsardom of Russia and the subsequent Russian Empire from 1713 to 1918 . After the October Revolution in 1917, the Bolsheviks moved their government to Moscow.As one of the most important tourism centers in Russia, Saint Petersburg received over 15 million tourists in 2018, and is considered an important economic, scientific and cultural centre of Russia. In modern times, it is considered the Northern Capital and serves as a home to some federal government bodies such as the Constitutional Court of Russia and the Heraldic Council of the President of the Russian Federation. It is also a seat for the National Library of Russia and a planned location for the Supreme Court of the Russian Federation, as well as the home to the headquarters of the Russian Navy, and the Western Military District of the Russian Armed Forces. The Historic Centre of Saint Petersburg and Related Groups of Monuments constitute a UNESCO World Heritage Site, so it is also referred to as Russia's cultural capital. Saint Petersburg is home to the Hermitage, one of the largest art museums in the world, and the Lakhta Center, the tallest skyscraper in Europe. Many foreign consulates, international corporations, banks and businesses have offices in Saint Petersburg.