Myanmar, officially the Republic of the Union of Myanmar, formerly known as Burma, is a country in Southeast Asia. It is the largest country in Mainland Southeast Asia, and has a population of about 54 million as of 2017. Myanmar is bordered by Bangladesh and India to its northwest, China to its northeast, Laos and Thailand to its east and southeast, and the Andaman Sea and the Bay of Bengal to its south and southwest. The country's capital city is Naypyidaw, and its largest city is Yangon. Early civilisations in the area included the Tibeto-Burman-speaking Pyu city-states in Upper Myanmar and the Mon kingdoms in Lower Myanmar. In the 9th century, the Bamar people entered the upper Irrawaddy valley, and following the establishment of the Pagan Kingdom in the 1050s, the Burmese language, culture, and Theravada Buddhism slowly became dominant in the country. The Pagan Kingdom fell to Mongol invasions, and several warring states emerged.