The thumb-shaped state is characterized by wholly mountainous terrain. Almost the entire state is hilly, with an elevation ranging from 280 metres (920 ft) to 8,585 metres (28,000 ft). The summit of the Kangchenjunga is the highest point which falls on the border between Sikkim and Nepal. For the most part, the land is unfit for agriculture because of the precipitous and rocky slopes. However, certain hill slopes have been converted into farm lands using terrace farming techniques. Numerous snow-fed streams in Sikkim have carved out river valleys in the west and south of the state. These streams combine into the Teesta and its tributary, the Rangeet. The Teesta, described as the "lifeline of Sikkim", flows through the state from north to south. About a third of the land is heavily forested.
The Himalayan ranges surround the northern, eastern and western borders of Sikkim in a crescent. The Lower Himalayas in the southern reaches of the state are the most densely populated. The state has 28 mountain peaks, more than 80 glaciers, 227 high-altitude lakes including the Tsongmo Lake, Gurudongmar and Khecheopalri Lake, 5 hot springs, and more than 100 rivers and streams. Eight mountain passes connect the state to Tibet, Bhutan and Nepal.
Unfrozen Gurudongmar Lake in North Sikkim
Sikkim's hot springs are known for medicinal and therapeutic values. The most important hot springs are at Phurchachu (Reshi), Yumthang, Borang, Ralang, Taram-chu and Yumey Samdong. They have high sulphur content and are located near river banks. Some also emit hydrogen. The average temperature of the water in these hot springs is 50 °C (122 °F).