Allahabad (pronunciation ), officially known as Prayagraj, and also known as Illahabad and Prayag, is a city in the Indian state of Uttar Pradesh. It is the administrative headquarters of Allahabad district—the most populous district in the state and 13th most populous district in India—and the Allahabad division. The city is the judicial capital of Uttar Pradesh with Allahabad High Court being the highest judicial body in the state. As of 2011, Allahabad is the fifth most populous city in the state, eighth in Northern India and twenty-fourth in India, with an estimated population of 1.11 million in the city and 1.21 million in its metropolitan region. In 2011 it was ranked the world's 40th fastest-growing city. Allahabad, in 2016, was also ranked the third most liveable city in the state (after Noida and Lucknow) and sixteenth in the country. The city experiences one of the highest levels of air pollution worldwide, with the 2016 update of the World Health Organization's Global Urban Ambient Air Pollution Database finding Allahabad to have the third highest mean concentration of "PM2.5" (<2.5 μm diameter) particulate matter in the ambient air among all the 2972 cities tested (after Zabol and Gwalior).The city lies close to Triveni Sangam, "three-river confluence", original name – Prayag, "place of sacrifice or offering" – which lies at the sangam (confluence) of the Ganga, Yamuna and Sarasvati rivers, a propitious place to conduct sacrifices. It plays a central role in Hindu scriptures. Allahabad was originally called Kaushambi (now a separate district) by the Kuru rulers of Hastinapur, who developed it as their capital. Since then, the city has been a political, cultural and administrative centre of the Doab region. In the early 17th century, Allahabad was a provincial capital in the Mughal Empire under the reign of Jahangir.Akbarnama mentions that the Mughal emperor Akbar founded a great city in Allahabad. `Abd al-Qadir Bada'uni and Nizamuddin Ahmad mention that Akbar laid the foundations of an imperial city there which was called Ilahabas or Ilahabad. He was said to be impressed by its strategic location and built a fort there, later renaming it Ilahabas by 1584 which was changed to Allahabad by Shah Jahan.In 1580, Akbar created the "Subah of Ilahabas" with Allahabad as its capital. In mid-1600, Salim had made an abortive attempt to seize Agra's treasury and came to Allahabad, seizing its treasury and setting himself up as a virtually independent ruler. He was, however, reconciled with Akbar and returned to Allahabad where he stayed before returning to the royal court in 1604.In 1833 it became the seat of the Ceded and Conquered Provinces region before its capital was moved to Agra in 1835. Allahabad became the capital of the North-Western Provinces in 1858 and was the capital of India for a day. The city was the capital of the United Provinces from 1902 to 1920 and remained at the forefront of national importance during the struggle for Indian independence.Located in southern Uttar Pradesh, the city's metropolitan area covers 70.5 km2 (27.22 sq miles). Although the city and its surrounding area are governed by several municipalities, a large portion of Allahabad District is governed by the Allahabad City Council. The city is home to colleges, research institutions and 2 dozen central and state government offices. Allahabad has hosted cultural and sporting events, including the Prayag Kumbh Mela and the Indira Marathon. Although the city's economy was built on tourism, most of its income now derives from real estate and financial services. The Allahabad district is the second-most revenue providing district in Uttar Pradesh.

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