Ü-Tsang or Tsang-Ü is one of the four traditional provinces of Tibet, the others being Amdo in the north-east, Kham in the east and Ngari (including former Guge kingdom) in the north-west. Geographically Ü-Tsang covered the south-central of the Tibetan cultural area, including the Brahmaputra River watershed. The western districts surrounding and extending past Mount Kailash are included in Ngari, and much of the vast Changtang plateau to the north. The Himalayas defined Ü-Tsang's southern border. The present Tibet Autonomous Region corresponds approximately to what was ancient Ü-Tsang and western Kham.