Lake Päijänne is the second largest lake in Finland (1,080 km2 (266,874 acres)). The lake drains into the Gulf of Finland via the Kymi River. The major islands are from north to south Vuoritsalo, Muuratsalo, Onkisalo, Judinsalo, Edessalo, Taivassalo, Haukkasalo, Vehkasalo, Mustassalo, Virmailansaari and Salonsaari. The largest island is Virmailansaari. The word saari means an island. Salo meant before a great island, nowadays it means a great forest area.
Largest cities on the shores of Päijänne are Jyväskylä in the North and Lahti in the South.
An underground aqueduct, Päijänne Water Tunnel, connects the lake to Helsinki, providing the capital area with water. The deepest point in any lake in Finland is located in Päijänne (95.3 m).