The county comprises the upper valley of the Bum-chu or Arun River, with the valleys of its tributaries plus the valleys of the Rongshar Tsangpo and the Lapchi Gang Tsanpo which flow south into Nepal. It is bordered on the south by the main range of the Himalayas including Mount Everest (Tib. Chomolungma), Makalu and Cho Oyu. The present county administration is located at Shelkar, about east of Tingri (town).