Tibet is a plateau region in Central Asia and the home to the indigenous Tibetan people. With an average elevation of 4,900 metres (16,000 ft), it is the highest region on Earth and is commonly referred to as the "Roof of the World." Geographically, UNESCO and Encyclopædia Britannica[1] consider Tibet to be part of Central Asia, while several academic organizations controversially consider it part of South Asia. Many parts of the region were united in the seventh century by King Songtsän Gampo. Power eventually shifted to the Dalai Lama, a position that combined spiritual and political power. Between the 17th century and 1951, the Dalai Lama and his regents were the predominant political power administering religious and administrative authority[2] over large parts of Tibet from the traditional capital Lhasa.