Danau Toba and the surrounding countryside is one of the most beautiful areas in Southeast Asia. The cool climate, pine-clothed mountain slopes, the lake and the sprinkling of church spires give the area an almost alpine flavour. After Medan or Padang, it is a welcome relief from the bustle, heat and humidity of the lowlands. The vast inland lake lies 160 km south of Medan and forms the core of Batakland in both a legendary and a geographical sense. The lake covers a total of 1707 sq km and is the largest inland body of water in Southeast Asia (87 km long and 31 km across at its widest point). Lodged in the centre of the lake is Samosir Island, one of Sumatra's most popular destinations.
Danau Toba was formed after a massive volcanic explosion 75,000 years ago, not dissimilar - although far more violent - to the one that vaporized Krakatoa in the late 19th century. The eruption of Toba is thought to have been the most powerful eruption in the last million years. The area is now volcanically dormant, the only indication of latent activity being the hot springs on the hill overlooking Pangururan . The fact that Danau Toba's water is so warm for a lake at close to 1000 m leads one to assume that there must be some heat underwater too.