The kingdom of Bhutan lies deep in the eastern Himalayas. It is surrounded by the Tibet Autonomous Region (TAR) of China to the north, and the Indian territories of Assam and West Bengal to the south, Arunachal Pradesh to the east and Sikkim to the west. The tiny landlocked kingdom has a total area of about 47,000 square kilometers and spreads between meridians 89°E and 93°E, and latitudes 27°N and 29°N. Bhutan features three major geographic regions, namely, the high Himalayas of the north, the hills and valleys of the interior, and the foothills and plains of the south. While the towering Himalayan mountains of Bhutan dominate the north of the country, where peaks can easily reach 7,000 metres (22,966 ft) above the sea level, in the south, the Duar Plain drops sharply away from the Himalayas into the large tracts of semi-tropical forest, grasslands and bamboo jungle. Within the mainland of Bhutan, the valleys of different heights and topography makes the country an ideal place for both native people and tourists. The valleys of Bhutan are traversed by the country’s four major river systems and their tributaries which ultimately drain to the Brahmaputra River in India. The valleys are linked by a series of passes (called "La" in Dzongkha, the national language of Bhutan). Between the Haa valley and Paro Valley is the Chele La (3,780 metres (12,402 ft)). The Chele La is the highest pass crossed by a Bhutanese highway. The Lateral Road from Thimphu to Punakha crosses the Dochu La (3,116 metres (10,223 ft)), which features 108 chortens built to commemorate the expulsion of Assamese guerrillas. East of Wangdue Phodrang is the Pele La (3,390 metres (11,122 ft)). Continuing to the east along the main highway, other major passes include the Yotang La, Thrumshing La and Kori La (2,298 metres (7,539 ft).