Visit Lake Toba, the Largest Lake in Indonesia

Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano,

100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft). It is the largest lake in Indonesia and the largest volcanic lake in the world.
Lake Toba is the site of a supervolcanic eruption that occurred 69,000-77,000 years ago, a massive climate-changing event.
The eruption is believed to have had a VEI intensity of 8.

It is believed to be the largest explosive eruption anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today.

This theory however, has been largely debated as there is no evidence for any other animal decline or extinction, even in environmentally sensitive species.
However, it has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decline in temperatures between 3-5 degrees C, and up to 15 degrees C in higher latitudes.
(Wikipedia.org)