evidence: Fergana Valley, enormous depression between the Tien Shan and Gissar and Alay mountain systems, lying mainly in eastern Uzbekistan and partly in Tajikistan and Kyrgyzstan. The roughly triangular valley has an area of 8,500 square miles (22,000 square km). It is bordered on the northwest by the Chatkal and Kurama mountains, on the northeast by the Fergana Mountains, and on the south by the Alay and Turkistan ranges, which rise to more than 16,500 feet (5,000 metres). In the west it is linked to the Mirzachül (Myrzashöl) steppe by the narrow Khujand Gates. [...] The Fergana Valley is one of the most densely populated areas of Central Asia and is a major producer of cotton, fruit, and raw silk. Among the mineral deposits that are exploited are coal, oil, mercury, antimony, and ozocerite. The chief cities are Khujand, Kokand (Quqŏn), Fergana, Marghilon, Andijon, and Namangan. Sedentary agriculture has been practiced for many centuries in the Fergana Valley, which also lay on one of the main trade routes to China. The valley was conquered by the Arabs in the 8th century, by Genghis Khan in the 13th, and by Timur (Tamerlane) in the 14th. The khans of Kokand ruled it from the late 18th century until it was taken by Russia in 1876.