Parts of the Pamir and Trans-Alai mt. systems are in the east, and the highest peaks in the country are Ismoili Somoni Peak (24,590 ft/7,495 m) and Lenin Peak, formerly Kaufmann Peak (23,405 ft/7,134 m). The southeast is occupied by an arid plateau c.12,000 to 15,000 ft (3,660–4,570 m) high. The only extensive low districts are the Tajik section of the Fergana Valley in the north and the hot, dry Gissar and Vakhsh valleys in the southwest. In the Fergana Valley, there are two small exclaves of Tajikistan, one surrounded by Kyrgyzstan, the other by Uzbekistan. The Amu Darya, Syr Darya, and Zeravshan are the chief rivers and are used for irrigation. Dams and irrigation projects, notably the Nurek dam and the Great Gissar Canal, have opened almost 1 million acres (400,000 hectares) of land to cultivation and also provide hydroelectric power, but the country experiences critical energy shortages in the winter when water levels are lower. In addition to the capital of Dushanbe, other important cities are Khudjand, Uroteppa, and Qŭrghonteppa.
Most of Tajikistan's people are concentrated in its narrow, deep intermontane valleys. About 80% of the population is composed of Tajiks (also spelled Tadjiks or Tadzhiks), a Sunni Muslim people who speak a language virtually indistinguishable from Persian (Farsi). The rest of the people are mainly Uzbeks (15%), Russians, Kyrgyz, and others. Tajik is the official language. Russian, once widely spoken as an interethnic common language, has become less prevalent since independence.