Lake Ladoga
Around 9000 BP Ancylus Lake, another stage of the Baltic Sea, retreated, and many lowland lakes were also isolated in depressions formed earlier by glacial exaration and fluvioglacial activity. Lake Ladoga was separated from the sea as well. Due to land uplift, around 5000 BP the River Vuoksi started emptying into Lake Ladoga as a new outlet of Lake Saimaa. Lake Ladoga transgressed, flooding lowland lakes and the Vuoksi, and became connected with the sea at Heinjoki (now Veshchevo), to the east of present-day Vyborg. Around 3100–2400 BP the Neva River emerged, draining Lake Ladoga into the Baltic Sea. Ladoga level gradually sank from 15–18 m to its modern position of 4–5 m above sea-level, and lowland lakes were isolated again. However, the Vuoksi still had a significant direct outflow connection to the Bay of Vyborg, possibly as late as in the 12th century AD. The connection disappeared due to ongoing land uplift in the 2nd millennium AD.