Saint Petersburg, formerly known as Petrograd and later Leningrad, is the second-largest city in Russia. It is situated on the Neva River, at the head of the Gulf of Finland on the Baltic Sea, with a population of roughly 5.4 million residents. Saint Petersburg is the fourth-most populous city in Europe, the most populous city on the Baltic Sea, as well as the world's northernmost city with over 1 million residents.