Nestling as it does in the Himalayan mountains, the state of Sikkim is characterised by mountainous terrain. Almost the entire state is hilly, with an elevation ranging from 280 metres (920 ft) to 8,586 metres (28,169 ft). The summit of Kangchenjunga—the world’s third-highest peak—is the state’s highest point, situated on the border between Sikkim and Nepal. For the most part, the land is unfit for agriculture because of the rocky, precipitous slopes. However, some hill slopes have been converted into terrace farms. Numerous snow-fed streams have carved out river valleys in the west and south of the state. These streams combine into the major Teesta River and its tributary, the Rangeet, which flow through the state from north to south. About a third of the state is heavily forested.