Lake Toba (or Danau Toba in Indonesian) is a lake and supervolcano, 100 kilometres long and 30 kilometres wide, and 505 metres at its deepest point. Toba is Located in the middle of the northern part of Sumatra  with a surface elevation of about 900 metres. It is the largest volcanic lake in the world.

The term Batak designates any one of several groups inhabiting the interior of Sumatera Utara Province south of Aceh: Angkola, Karo, Mandailing, Pakpak, Simelungen, Toba, and others. The Batak number around 3 million. Culturally, they lack the complex etiquette and social hierarchy of the Hinduized peoples of Indonesia.