<P> Qutab 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. Sher Shah suri also added an entrance to this tower while he was ruling and Humayun was at an exile . </P> <P> It derived its name from the Sufi saint Qutbuddin Bakhtiar Kaki whom Qutab Ud - Din - Aibak revered . The Minar is surrounded by several historically significant monuments of the Qutab 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> <P> Qutab Minar was established along with Quwwat - ul - Islam Mosque around 1192 by Qutab - ud - din Aibak, first ruler of the Delhi Sultanate . The mosque complex is one of the earliest that survives in the Indian subcontinent . The minaret is named after Qutab - ud - din Aibak, or Qutabuddin Bakhtiar Kaki, a Sufi saint . Its ground storey was built over the ruins of the Lal Kot, the citadel of Dhillika . Aibak's successor Iltutmish added three more storeys . The minar's topmost storey was damaged by lightning in 1369 and was rebuilt by Firoz Shah Tughlaq, who added another storey . In 1505, an earthquake damaged Qutub Minar; it was repaired by Sikander Lodi . On 1 September 1803, a major earthquake caused serious damage . Major Robert Smith of the British Indian Army renovated the tower in 1828 and installed a pillared cupola over the fifth story, thus creating a sixth . The cupola was taken down in 1848, under instructions from The Viscount Hardinge, then Governor General of India . It was reinstalled at ground level to the east of Qutab Minar, where it remains . It is known as "Smith's Folly". </P> <P> The tower's style is basically Iranian, though likely patterned on Afghanistan's Minaret of Jam, and adapted to local artistic conventions by the incorporation of "looped bells and garlands and lotus borders into the carving". Aybak also started Qutub Minar along the patterns of Iranian minarets but built by Hindus artisans . Numerous inscriptions in Parso - Arabic and Nagari characters in different sections of the Qutab Minar reveal the history of its construction, and the later restorations and repairs by Firoz Shah Tughluq (1351--89) and Sikandar Lodi (1489--1517). </P>

Who built the fifth floor of qutub minar