in the eastern oblast forms part of the divide between the Baltic Sea and Caspian Sea basins.

The terrain of Leningrad Oblast is relatively flat and mostly covered with forest and swamps. An exception is the rocky Karelian Isthmus, which contains a lake district, as well as the Vepsian Upland in the east. The biggest lakes on the isthmus are Lake Vuoksa, Lake Sukhodolskoye,