Saimaa (sī´mä), lake system c.1,850 sq mi (4,790 sq km), occupying the heavily glaciated plateau of S central Finland. It comprises more than 120 connecting lakes; the large southern basin of the system constitutes Lake Saimaa proper (c.500 sq mi/1,290 sq km). The system drains SE into Lake Ladoga (Russia) through the Vuoskijoki (c.100 mi/160 km long). There are numerous canals to facilitate steamship and lumber-raft traffic through the Saimaa Canal (c.37 mi/60 km long; completed 1856), which terminates at Vyborg, Russia, on the Gulf of Finland. The cities of Joensuu, Kuopio, Lappeenranta, and Mikkeli are on the lakes.