Delhi, also known as the National Capital Territory of India is the capital of India. 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 nearly 27 million residents as of 2014,[3] and is the largest urban agglomeration in India by land area and population. It is also the 2nd most populous city on the planet.[4][5] The NCT and its urban region have been given the special status of National Capital Region (NCR) under the Constitution of India's 69th amendment act of 1991. The NCR includes the neighbouring cities of Gurgaon, Noida, Ghaziabad, Faridabad,Greater Faridabad called as Neharpar, Greater Noida,Sonepat, Panipat, Karnal, Rohtak, Rewari, Baghpat, Meerut, Alwar, Bharatpur and other nearby towns.

Delhi was the site of ancient Indraprastha (Khandavprastha), the ancient capital of the Pandavas during the Mahabharata.[7] Delhi re-emerged as a major political, cultural and commercial city along the trade routes between northwest India and the Gangetic plainduring the Delhi Sultanate era.

Delhi is the largest commercial centre in northern India; it has an estimated net State Domestic Product (FY 2010) of  1578 billion (US$26 billion) in nominal terms and ~ 6300 billion(US$100 billion) in PPP terms.[99] As of 2013, the per capita income of Delhi was Rs. 210000, highest in India. GSDP in Delhi at the current prices for 2012-13 is estimated at Rs 3.66 trillion (short scale) against Rs 3.11 trillion (short scale) in 2011-12.

List of twin towns and sister cities in India
Outline of India
List of tallest buildings in Delhi
Walking tours for Delhi promoted by Ministry of Tourism India