Danau Toba is the largest lake in all of Southeast Asia. The giant lake sits at an altitude of 800 meters, and is 100 kilometers long and 30 kilometers wide. The lake is situated in the caldera of the huge Toba volcano which erupted approximately 75,000 years ago. The eruption of Toba was one of the most massive eruptions ever on Earth. Many scientists believe that this eruption triggered the last ice age. The eruption probably lasted two weeks until finally the volcano collapsed and formed the caldera which is now Danau Toba. The bottom of the volcano rose and formed the island of Samosir which is beautifully situated in the middle of the blue waters of Toba.
source by en.wikipedia.org/wiki/Lake_Toba