Bangladesh (বাংলাদেশ, pronounced as [banglaˌdeS]), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 163 million people in an area of either 148,460 square kilometer (57,320 sq mi) or 147,570 square kilometer (56,980 sq mi) making it one of the most densely populated countries in the world. Bangladesh shares land borders with India to the west, north, and east, Myanmar to the southeast, and the Bay of Bengal to the south. It is narrowly separated from Nepal and Bhutan by the Siliguri Corridor; and from China by the Indian state of Sikkim in the north, respectively. Dhaka, the capital and largest city, is the nation's economic, political, and cultural hub. Chittagong, the largest seaport, is the second-largest city. Bangladesh forms the larger and eastern part of the Bengal region. According to the ancient Indian texts, Rāmāyana and Mahābhārata, the Vanga Kingdom, one of the namesakes of the Bengal region, was a strong naval power. In the ancient and classical periods of the Indian subcontinent, the territory was home to many principalities, including the Pundra, Gangaridai, Gauda, Samatata, and Harikela. It was also a Mauryan province under the reign of Ashoka. The principalities were notable for their overseas trade, contacts with the Roman world, the export of fine muslin and silk to the Middle East, and spreading of philosophy and art to Southeast Asia. The Gupta Empire, Pala Empire, the Chandra dynasty, and the Sena dynasty were the last pre-Islamic Bengali middle kingdoms. Islam was introduced during the Pala Empire, through trade with the Abbāsid Caliphate, but following the Ghurid conquests led by Bakhtiyār Khaljī, the establishment of the Delhi Sultanate and preaching of Shah Jalāl in the north-east, it spread across the entire region. In 1576, the wealthy Bengal Sultanate was absorbed into the Mughal Empire, but its rule was briefly interrupted by the Sūr Empire.