Bhutan is located on the southern slopes of the eastern Himalayas, landlocked between the Tibet Autonomous Region to the north and the Indian states of Sikkim, West Bengal, Assam and Arunachal Pradesh to the west and south. It lies between latitudes 26°N and 29°N, and longitudes 88°E and 93°E. The land consists mostly of steep and high mountains crisscrossed by a network of swift rivers, which form deep valleys before draining into the Indian plains. Elevation rises from 200 m (660 ft) in the southern foothills to more than 7,000 m (23,000 ft). This great geographical diversity combined with equally diverse climate conditions contributes to Bhutan's outstanding range of biodiversity and ecosystems.