The latter range is separated from the Karakorum Mountains by the deeply trenched gorge of the Raskem or Yarkand-darya, while the deep glen of the Kara-kash or Khotan-darya intervenes between the upper (Sughet Mountains) and the lower (Kilian Mountains) border-ranges.
It comprises the valleys of the Tekez (middle and lower portion), Kunghez, the Ili as far as the Russian frontier and its tributary, the Kash, with the slopes of the mountains turned towards these rivers.
The valley of the Kash is about 160 m.
The Avral Mountains, which separate the Kash from the Kunghez, are lower, but rocky, naked and difficult of access.
The oasis contains two small towns, Kara-kash and Yurun-kash, and over 300 villages, its total population being about 150,000.
The Khotan-Darya rises in the Kuen-lun Mountains in two headstreams, the Kara-kash and the Yurun-kash, which unite towards the middle of the desert, some 90 m.
The more southerly of the twin ranges, the Avral-tau, in which is the Arystan-daban pass at an altitude of 10,800 ft., terminates in 82° E., over against the confluence of the Kash and the Kunghez (Ili) rivers.