Lake Toba (Danau Toba) is the largest lake in South East Asia and is located in Sumatra, Indonesia. Samosir island within the lake is the island within the island of Sumatra.

Lake Toba is an immense volcanic lake covering area 1707 sq km (bigger than Singapore) with an island in the center. Formed by a gigantic volcanic eruption some 70,000 years ago, it is probably the largest resurgent caldera on Earth. Some studies say it might have been associated with causing previous ice age/climate change and the largest human population bottleneck ever. The island in the middle - Pulau Samosir - was joined to the caldera wall by a narrow isthmus, which was cut through to enable boats to pass; a road bridge crosses the cutting. Samosir island is the cultural centre of Batak tribe who are mostly Christians in the modern days. Traditional Batak houses are noted for their distinctive roofs (which curve upwards at each end, as a boat's hull does) and their colorful decor.

It is a great laid back place to chill out for a few days after jungle trekking. There are hot springs on the western side of the island just across the causeway from Pangururan. The water is hot. Locals usually use their hands to get some water out of the pool, standing in the pool is possible, but you probably won't be able to swim.