Gulf of Finland in the context of "Neva Bay"

Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, opposite Estonia. Finland has a population of 5.6 million, the majority being ethnic Finns. Its capital and largest city is Helsinki. The official languages are Finnish and Swedish, the mother tongues of 84.1 percent and 5.1 percent of the population, respectively. Finland's climate varies from humid continental in the south to boreal in the north. Its land is predominantly covered by boreal forest, with over 180,000 recorded lakes.

Finland was first settled around 9000 BC after the last Ice Age. During the Stone Age, various cultures emerged, distinguished by different styles of ceramics. The Bronze Age and Iron Ages were marked by contacts with other cultures in Fennoscandia and the Baltic region. From the late 13th century, Finland became part of Sweden following the Northern Crusades. In 1809, as a result of the Finnish War, Finland was captured from Sweden and became an autonomous grand duchy within the Russian Empire. During this period, Finnish art flourished and an independence movement gradually developed.

Helsinki (Swedish: Helsingfors) is the capital and most populous city in Finland. It is on the shore of the Gulf of Finland and is the seat of southern Finland's Uusimaa region. About 690,000 people live in the municipality, with 1.3 million in the capital region and 1.6 million in the metropolitan area. As the most populous urban area in Finland, it is the country's most significant centre for politics, education, finance, culture, and research. Helsinki is 80 kilometres (50 mi) north of Tallinn, Estonia, 400 kilometres (250 mi) east of Stockholm, Sweden, and 300 kilometres (190 mi) west of Saint Petersburg, Russia.

Together with the cities of Espoo, Vantaa and Kauniainen—and surrounding commuter towns, including the neighbouring municipality of Sipoo to the east—Helsinki forms a metropolitan area. This area is often considered Finland's only metropolis and is the world's northernmost metropolitan area with over one million inhabitants. Additionally, it is the northernmost capital of an EU member state. Helsinki is the third-largest municipality in the Nordic countries, after Stockholm and Oslo. Its urban area is the third-largest in the Nordic countries, after Stockholm and Copenhagen. Helsinki Airport, in the neighbouring city of Vantaa, serves the city with frequent flights to numerous destinations in Europe, North America, and Asia.

Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Russia. The territory of Estonia consists of the mainland, the larger islands of Saaremaa and Hiiumaa, and over 2,300 other islands and islets on the east coast of the Baltic Sea. Its capital Tallinn and Tartu are the two largest urban areas. The Estonian language, of the Finnic family, is the official language and the first language of the majority of its population of nearly 1.4 million. Estonia is one of the least populous members of the European Union and NATO.

Present-day Estonia has been inhabited since at least 9,000 BC. The medieval indigenous population of Estonia was one of the last pagan civilisations in Europe to adopt Christianity following the Northern Crusades in the 13th century. After centuries of successive rule by the Teutonic Order, Denmark, Sweden, and the Russian Empire, a distinct Estonian national identity began to emerge in the mid-19th century. This culminated in the 1918 Estonian Declaration of Independence from the then-warring Russian and German empires. Democratic throughout most of the interwar period, Estonia declared neutrality at the outbreak of World War II, but the country was repeatedly invaded and occupied, and ultimately annexed into the USSR. Throughout the de facto Soviet occupation, from World War II until 1991, Estonia's de jure state continuity was preserved by diplomatic representatives and the government-in-exile. Following the 1988–90 "Singing Revolution" against Soviet rule, full independence was restored on 20 August 1991.

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 Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North and Central European Plain regions. It is the world's largest brackish water basin.

The sea stretches from 53°N to 66°N latitude and from 10°E to 30°E longitude. It is a shelf sea and marginal sea of the Atlantic with limited water exchange between the two, making it an inland sea. The Baltic Sea drains through the Danish straits into the Kattegat by way of the Øresund, Great Belt and Little Belt. It includes the Gulf of Bothnia (divided into the Bothnian Bay and the Bothnian Sea), the Gulf of Finland, the Gulf of Riga and the Bay of Gdańsk.

Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.

"Sonar" can refer to one of two types of technology: passive sonar means listening for the sound made by vessels; active sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and sodar (an upward-looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.

The trade route from the Varangians to the Greeks was a medieval trade route that connected Scandinavia, Kievan Rus' and the Eastern Roman Empire. The route allowed merchants along its length to establish a direct prosperous trade with the Empire, and prompted some of them to settle in the territories of present-day Belarus, Russia and Ukraine. The majority of the route comprised a long-distance waterway, including the Baltic Sea, several rivers flowing into the Baltic Sea, and rivers of the Dnieper river system, with portages on the drainage divides. An alternative route was along the Dniester river with stops on the western shore of Black Sea. These more specific sub-routes are sometimes referred to as the Dnieper trade route and Dniester trade route, respectively.

The route began in Scandinavian trading centers such as Birka, Hedeby, and Gotland, the eastern route crossed the Baltic Sea, entered the Gulf of Finland, and followed the Neva River into Lake Ladoga. Then it followed the Volkhov River upstream past the towns of Staraya Ladoga and Novgorod (where it met the Volga trade route and which became a major trade centre), crossed Lake Ilmen, and continued up the Lovat River, the Kunya River and possibly the Serezha River [ru]. From there, a portage led to the Toropa River [ru] and downstream to the Western Dvina River. From the Western Dvina, the ships went upstream along the Kasplya River and were portaged again to the Katynka River (near Katyn), a tributary of the Dnieper. It seems probable that once the route was established, the goods were unloaded onto land transport to cross the portage and reloaded onto other waiting ships on the Dnieper. Along the Dnieper, the route crossed several major rapids and passed through Kiev. After entering the Black Sea, it followed its west coast to Constantinople.

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.