Saint Petersburg, formerly known as Petrograd, then Leningrad, is a city situated 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 over 5.3 million inhabitants as of 2018, it is the fourth-most populous city in Europe. An important Russian port on the Baltic Sea, it has a status of a federal subject.The city was founded by Tsar Peter the Great on 27 May [O.S. 16 May] 1703, on the site of a captured Swedish fortress. It served as a capital of the Russian Tsardom and the subsequent Russian Empire from 1713 to 1918. After the October Revolution, the Bolsheviks moved their government to Moscow.