Päijänne is the second biggest lake of Finland. It stretches from middle of country to only bit over hundred kilometers from Helsinki and Baltic sea.
Its importance is huge due to fact that almost whole Helsinki region takes water from there via a 120 km long tunnel.

The outlet of Päijänne runs towards east at north side of Salpausselkä, a long ridge which goes through whole Finland, and eventually breaks through it and forms Kymijoki river which runs to Baltic sea at Ruotsinpyhtää.

- area 1 116 km^2
- length 120 km
- average depth 17 m
- maximum depth 94,5 m
- coastline 11 140 km
- islands 1 886