River Neva in the context of "Saint Petersburg, Russia"

Saint Petersburg, formerly known as Petrograd and later Leningrad, is the second-largest city in Russia after Moscow. It is situated on the River Neva, at the head of the Gulf of Finland on the Baltic Sea. With an area of 1,439 sq km (556 sq mi), Saint Petersburg is the smallest administrative division of Russia by area. The city had a population of 5,601,911 residents as of 2021, with more than 6.4 million people living in the metropolitan area. Saint Petersburg is the fourth-most populous city in Europe, the most populous city on the Baltic Sea, and the world's northernmost city of more than 1 million residents. As the former capital of the Russian Empire, and a historically strategic port, 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 the apostle Saint Peter. In Russia, 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 1712 to 1918 (being replaced by Moscow for a short period between 1728 and 1730). After the October Revolution in 1917, the Bolsheviks moved their government to Moscow. The city was renamed Leningrad after Lenin's death in 1924. It was the site of the siege of Leningrad during World War II, the most lethal siege in history. In June 1991, only a few months before the Belovezha Accords and the dissolution of the Soviet Union, voters in a city-wide referendum supported restoring the city's original name.

The Karelian Isthmus (Russian: Карельский перешеек, romanized: Karelsky peresheyek; Finnish: Karjalankannas; Swedish: Karelska näset) is the approximately 45–110-kilometre-wide (30–70 mi) stretch of land situated between the Gulf of Finland and Lake Ladoga in northwestern Russia, to the north of the River Neva. Its northwestern boundary is a line from the Bay of Vyborg to the westernmost point of Lake Ladoga, Pekonlahti. If the Karelian Isthmus is defined as the entire territory of present-day Saint Petersburg and Leningrad Oblast to the north of the Neva and also a tiny part of the Republic of Karelia, the area of the isthmus is about 15,000 km (5,800 sq mi).

The smaller part of the isthmus to the southeast of the old Russia-Finland border is considered historically as Northern Ingria, rather than part of the Karelian Isthmus itself. The rest of the isthmus was historically a part of Finnish Karelia. This was conquered by the Russian Empire during the Great Northern War in 1712 and included within the autonomous Grand Duchy of Finland (1809–1917) of the Russian Empire. When Finland became independent in 1917, the isthmus (except for the territory roughly corresponding to present-day Vsevolozhsky District and some districts of Saint Petersburg) remained Finnish. Finnish Karelia was partly ceded to the Soviet Union by Finland following the Winter War (1939–1940) and Continuation War (1941–1944). In 1940–1941, during the Interim Peace, most of the ceded territories in the isthmus were included within the Karelo-Finnish SSR. However, since World War II the entire isthmus has been divided between the city of Saint Petersburg (mostly Kurortny District), as well as Priozersky District, Vsevolozhsky District and Vyborgsky District of Leningrad Oblast.