Delhi is the second largest metropolis of India, with a population of 17 million, and a federally-administered union territory officially known as the National Capital Territory of Delhi (NCT). Located on the banks of the Yamuna River in northern India, archaeological evidence suggest that Delhi has been continuously inhabited since at least 6th century BC.
Delhi has been the capital of several Indian empires in medieval period and a major city along the old trade routes between northwest India and the Indo-Gangetic Plains. It is the site of many ancient and medieval monuments, archaeological sites and remains. In 1639, Mughal emperor Shahjahan built a new walled city in Delhi which served as the capital of the Mughal Empire from 1649 to 1857.