lake toba is an immense volcanic lake covering an area of 1,707 km² (1,000 km² bigger than singapore) with an island in its centre. actually, lake toba is located in prapat area in north sumatra.
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. genetic estimates suggests that there were only a few thousand individuals that survived its catastrophic eruption.
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 the batak tribe who are now mostly christians.
lake toba was perhaps once more popular than it is nowadays, but for many it remains a firm fixture on the banana pancake trail. it is a great laid back place to chill out for a few days after jungle trekking etc. the location is very popular with chinese tourists around chinese new year, when availability drops dramatically and accommodation costs sky rocket. (source : wikitravel.org)