Delhi, known locally as Dilli and also by the official name National Capital Territory of Delhi (NCT), is the largest metropolis by area and the second-largest metropolis by population in India. It is the eighth largest metropolis in the world by population with more than 12.25 million inhabitants in the territory and with over 15.9 million residents in the National Capital Region area (which also includes Noida, Gurgaon, Greater Noida, Faridabad and Ghaziabad).The name Delhi is often also used to include some urban areas near the NCT, as well as to refer to New Delhi, the capital of India, which lies within the metropolis. The NCT is a federally administered union territory.
Located on the banks of the River Yamuna, Delhi has been continuously inhabited since at least the 6th century BCE. 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.
After the British East India Company had gained control of much of India during the 18th and 19th centuries, Calcutta became the capital both under Company rule and under the British Raj, until George V announced in 1911 that it was to move back to Delhi. A new capital city, New Delhi, was built to the south of the old city during the 1920s. When India gained independence from British rule in 1947, New Delhi was declared its capital and seat of government. As such, New Delhi houses important offices of the federal government, including the Parliament of India, as well as numerous national museums, monuments, and art galleries.
Owing to the migration of people from across the country, Delhi has grown to be a multicultural, cosmopolitan metropolis. Its rapid development and urbanisation, coupled with the relatively high average income of its population, has transformed Delhi. Today, Delhi is a major cultural, political, and commercial center of India.
Delhi features an atypical version of a humid subtropical climate, with long very hot summers and brief mild winters. Summers are long and extremely hot, from early April to mid-October, with the monsoon season in between. Beginning of March sees a reversal in the direction of wind, from the north-western direction, to the south-western. These bring the hot waves from Rajasthan, carrying sand and are a characteristic of the Delhi summer. These are called loo. The months of March to May see a time of hot prickling heat. Monsoon arrives at the end of June, bringing some respite from the heat, but increasing humidity at the same time. Winter starts in late November and peaks in January and is notorious for its heavy fog. Extreme temperatures range from −0.6 °C (30.9 °F) to 44.5 °C (112.1 °F). The annual mean temperature is 25 °C (77 °F); monthly mean temperatures range from 13 °C to 32 °C (56 °F to 90 °F). The average annual rainfall is approximately 714 mm (28.1 inches), most of which is during the monsoons in July and August. The average date of the advent of monsoon winds in Delhi is 29 June.
The National Capital Territory of Delhi is spread over an area of 1,484 km2 (573 sq mi) , of which 783 km2 (302 sq mi) is designated rural, and 700 km2 (270 sq mi) urban. Delhi has a maximum length of 51.9 km (32 mi) and the maximum width of 48.48 km (30 mi). There are three local bodies (statutory towns) namely, Municipal Corporation of Delhi (area is 1,397.3 km2 or 540 sq mi), New Delhi Municipal Committee (42.7 km2 or 16 sq mi) and Delhi Cantonment Board (43 km2 or 17 sq mi).
Delhi is an expansive area, in its extremity it spans from Sarup Nagar in the north to Rajorki in the south. Najafghar is the furthest point west, and the river Yamuna is its (relatively conservative) eastern extremity. Places like Shahdara and Bhajanpura are its eastern ends and are one of major shopping centres in Delhi. The NCR encompasses points south and east of the said border, namely Noida and DLF.