Bhutan is on the southern slopes of the eastern Himalayas, landlocked between the Tibet Autonomous Region of China to the north and the Indian states of Sikkim, West Bengal, Assam to west and south and the Indian state of Arunachal Pradesh to the east. 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 that form deep valleys before draining into the Indian plains. Elevation rises from in the southern foothills to more than . This great geographical diversity combined with equally diverse climate conditions contributes to Bhutan's outstanding range of biodiversity and ecosystems.