Located in the middle of the northern part of the Indonesian island of Sumatra, Lake Toba is a large natural lake occupying the caldera of a supervolcano. The lake is about 100 kilometres long, 30 kilometres wide, and up to 505 metres deep. The Samosir Island situated inside the lake is bigger than Singapore. Lake Toba is the site of a massive supervolcanic eruption estimated around 74000 years ago.