Lake Matano, Tectonic lake in East Luwu Regency, South Sulawesi, Indonesia

Lake Matano is a tectonic lake in South Sulawesi with a surface area of around 160 square kilometers and clear water throughout. It reaches a maximum depth of 590 meters, making it Indonesia's deepest lake, and its shape was created by ancient geological movements.

Lake Matano formed in a tectonic graben around one to two million years ago, making it the oldest of the four lakes in the Malili system. Its basin lies on a strike-slip fault, and the lake is counted among the world's ancient lakes, a group that also includes Lake Poso, Lake Biwa and Lake Baikal.

Communities living around the shoreline practice traditional fishing methods and rely on wooden boats to move between settlements. This way of life shapes the character of the lake today and shows how people have depended on the water for generations.

The lake lies about 50 km from Malili, the capital of East Luwu Regency, and can be crossed by boat between Sorowako and Nuha, linking Morowali Regency with East Luwu. Basic accommodation and services are in Sorowako. The dry season, roughly April to October, gives the easiest road conditions.

The lower water layers of the lake differ dramatically from the upper zone and contain conditions similar to Earth's early oceans. There is almost no oxygen in these depths, while iron content is extremely high, making the water dark and dense.