Qutub Minar, behind the Alai Gate, is the tallest brick minaret in the world, and listed as a UNESCO World Heritage Site. The five stage minaret was ordered in 1193 by India's first Muslim ruler, the Sultan of Delhi, Qutb-ud-din Aibak, to exceed the Jam Minaret in Afghanistan, but during his lifetime only the 14.3 meter wide base was completed. The third Sultan, Iltutmish completed the middle three levels, and by 1368 Sultan Firuz Shah Tughlaq added the fifth level, measuring 2.75 metres diagonally and completing the Minaret to reach 72 metres high.
The entire structure is built with red sandstone bricks and some are likely to have been re-used from the ruins of Lal Kot, or the Red Citadel which stood here in the 6th century during the time of the last Chauhan Hindi rulers of Delhi. There are 379 steps leading to the topmost fifth level and each of the levels is separated by a muqarna or stalactite corbel, decorated by Cufic inscriptions from the Koran. Apart from being the most prominent, the Qutub Minar is also probably the best surviving example of the earliest Indo-Islamic architecture.
The Alai Gate, on the left, is a domed gateway that functions as the entrance to the Qutub complex was constructed by Ala-ud din Khilji, the first Khilji Sultan of Delhi in 1290. The dominating red engraved sandstone is refined with inlaid white marble, also finely detailed by Turkish craftsmen.