Sumatra contains Lake Toba, the world’s largest volcanic lake, in the island’s North Sumatra province.
Lake Toba occupies the caldera of a gigantic supervolcano. The major eruption that formed the lake occurred about 74,000 years ago and is regarded as one of the largest known explosive eruptions in Earth’s recent geological history. The caldera is roughly 100 kilometres long and 30 kilometres wide.
Samosir Island rises within Lake Toba and is connected to the surrounding land by a narrow isthmus. The region is traditionally associated with the Batak peoples, whose communities, architecture, music, and customs remain important parts of North Sumatra’s cultural identity.
Sumatra is Indonesia’s sixth-largest island and one of the world’s largest islands. It should not be confused with Java, which lies southeast across the Sunda Strait and contains Jakarta. Borneo is also part of Indonesia, but Lake Toba is specifically located on Sumatra.