Delhi officially the National Capital Territory of Delhi (NCT), is a metropolitan area located on the banks of the Yamuna in northern India and includes the Indian national capital city, New Delhi. Delhi is known to have 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, sacked and rebuilt several times, particularly during the medieval period, and therefore the modern conurbation of Delhi is a cluster of a number of cities spread across the metropolitan region. Delhi is believed to have been the site of Indraprastha, the legendary capital of the Pandavas during the times of the Mahabharata. Delhi re-emerged as a major political, cultural and commercial city along the trade routes between northwest India and the Gangetic plain during the period of the Delhi sultanates. The British captured Delhi in 1857 and the city replaced Kolkata as the seat of British government in India in 1911. Today Delhi contains many important historical monuments, buildings and features. Qutab Minar also known as Qutb Minar and Qutub Minar, is the tallest minaret in India, originally an ancient Islamic Monument, inscribed with arabic inscriptions, though the iron pillar has some bhramini inscriptions, and is a UNESCO World Heritage Site. Qutub Minar is made of red sandstone and marble. The tower has 379 stairs, is 72.5 metres high, and has a base diameter of 14.3 metres, which narrows to 2.7 metres at the top storey. Construction was started in 1192 by Qutub-ud-din Aibak and was completed by Iltutmish. The cancellation depicts Qutab Minar.