<Tr> <Th> Constructed by </Th> <Td> Started construction by Qutub - ud - din Aibak & completed construction by Iltutmish </Td> </Tr> <P> Qutub Minar is a minaret that forms part of the Qutb complex, a UNESCO World Heritage Site in the Mehrauli area of Delhi, India . Made of red sandstone and marble, Qutub Minar is a 73 - metre (240 feet) tall tapering tower of five storeys, with a 14.3 metre (47 feet) base diameter, reducing to 2.7 metres (9 feet) at the peak . It contains a spiral staircase of 379 steps . Its design is thought to have been based on the Minaret of Jam, in western Afghanistan . </P> <P> Qutb Ud - Din - Aibak, founder of the Delhi Sultanate, started construction of the Qutub Minar's first storey around 1192 . In 1220, Aibak's successor and son - in - law Iltutmish completed a further three storeys . In 1369, a lightning strike destroyed the top storey . Firoz Shah Tughlaq replaced the damaged storey, and added one more . </P> <P> The Minar is surrounded by several historically significant monuments of the Qutb complex, including Quwwat - ul - Islam Mosque, which was built at the same time as the Minar, and the much older Iron Pillar of Delhi . The nearby pillared Cupola known as "Smith's Folly" is a remnant of the tower's 19th century restoration, which included an ill - advised attempt to add a sixth storey . </P>

Who completed the qutub minar and in whose memory was it built
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