Delhi officially the National Capital Territory of Delhi, is the capital territory of India. Delhi is historically and culturally connected to both the Upper Doab of the Yamuna-Ganges river system and the Punjab region. It is bordered by Haryana on three sides and by Uttar Pradesh to the east. It is the largest city in India in terms of geographical area – about 1,484 square kilometres (573 sq mi). It has a population of about 16.3 million, making it the second most populous city and second most populous urban agglomeration in India and 3rd largest urban area in the world. Such is the nature of urban expansion in Delhi that its growth has expanded beyond the NCT to incorporate towns in neighbouring states and at its largest extent can count a population of about 25 million residents as of 2014.
Delhi has been continuously inhabited since the 6th century BC. Through most of its history, Delhi has served as a capital of various kingdoms and empires. It has been captured, ransacked and rebuilt several times, particularly during the medieval period, and modern Delhi is a cluster of a number of cities spread across the metropolitan region.