Located on the banks of river the Yamuna in the Haryana region of northern India, Delhi has been continuously inhabited since at least the 6th century BC, according to archaeological evidence. After the rise of the Delhi Sultanate, Delhi emerged as a major political, cultural and commercial city along the 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. ...that in 2004–05, there were 2,515 primary, 635 middle, 504 secondary and 1,208 senior secondary schools in Delhi. That year, the higher education institutions in the city included 165 colleges, among them five medical colleges and eight engineering colleges, six universities and nine deemed universities.