Bhutan (; ), officially the Kingdom of Bhutan (), is a landlocked country in South Asia. It is situated in the Eastern Himalayas, between China in the north and India in the south. A mountainous country, Bhutan is known locally as "Druk Yul" or "Land of the Thunder Dragon". Nepal and Bangladesh are located near Bhutan but do not share a land border with it. The country has a population of over 727,145 and territory of and ranks 133rd in terms of land area and 160th in population. Bhutan is a constitutional monarchy with a king (Druk Gyalpo) as the head of state and a prime minister as the head of government. Vajrayana Buddhism is the state religion and the Je Khenpo is the head of state religion. The subalpine Himalayan mountains in the north rise from the country's lush subtropical plains in the south. In the Bhutanese Himalayas, there are peaks higher than above sea level. Gangkhar Puensum is Bhutan's highest peak and is the highest unclimbed mountain in the world. The wildlife of Bhutan is notable for its diversity, including the Himalayan takin. The capital and largest city is Thimphu. Bhutan and neighbouring Tibet experienced the spread of Buddhism which originated in the Indian subcontinent during the lifetime of Gautama Buddha. In the first millennium, the Vajrayana school of Buddhism spread to Bhutan from the southern Pala Empire of Bengal. During the 16th century, Ngawang Namgyal unified the valleys of Bhutan into a single state. Namgyal defeated three Tibetan invasions, subjugated rival religious schools, codified the Tsa Yig legal system, and established a government of theocratic and civil administrators. Namgyal became the first Zhabdrung Rinpoche and his successors acted as the spiritual leaders of Bhutan like the Dalai Lama in Tibet. During the 17th century, Bhutan controlled large parts of northeast India, Sikkim and Nepal; it also wielded significant influence in Cooch Behar State. Bhutan ceded the Bengal Duars to British India during the Bhutan War in the 19th century. The House of Wangchuck emerged as the monarchy and pursued closer ties with the British in the subcontinent. In 1910, a treaty guaranteed British advice in foreign policy in exchange for internal autonomy in Bhutan. The arrangement continued under a new treaty with India in 1949 (signed at Darjeeling) in which both countries recognised each other's sovereignty. Bhutan joined the United Nations in 1971. It has since expanded