Lake Päijänne is the deepest and second largest lake in Finland. (1.080 km2, 266,874 acres). The lake drains into the Gulf of Finland via the Kymi River. There are 1886 islands in Lake Päijänne. The largest city on the shores of Päijänne is Jyväskylä in the North. The city of Lahti is connected to Päijänne through Lake Vesijärvi and Vääksy canal.
An underground aqueduct, Päijänne Water Tunnel, connects the lake to Vantaa, providing the Greater Helsinki area with water. Lake Päijänne is the deepest lake in Finland, with a depth of 95,3 m or (313 ft)
Sysmä is very blessed to be located on the south-eastern bank of Lake Päijänne. Even though there are 167 lakes located in Sysmä, Lake Päijänne is the most important.