The
Karelian Isthmus (; ) is the approximately 45–110 km wide stretch of land, situated between the
Gulf of Finland and
Lake Ladoga in northwestern
Russia, to the north of the
River Neva (between 61°21’N, 59°46’N and 27°42’E, 31°08’E). Its northwestern boundary is the relatively narrow area between the
Bay of Vyborg and Lake Ladoga. If the Karelian Isthmus is defined as the entire territory of present-day
Saint Petersburg and
Leningrad Oblast to the north of the Neva, the isthmus' area covers about 15,000 km
2.