Built in the early 13th century a few kilometres south of Delhi, the red sandstone tower of Qutb Minar is the highest tower in India. It has a diameter of 14.32 m at the base and about 2.75 m on the top with a height of 72.5 m.
Qutbu'd-Din Aibak laid the foundation of the minar in C.E.1199 for the use of the mu'azzin (crier) to give calls for prayer and raised the first storey, to which were added three more storeys by his successor and son-in-law, Shamsu'd-Din Iltutmish (AD 1211-36). The entire storey are surrounded by a projected balcony encircling the minar and supported by stone brackets, which are decorated with honey-comb design, more conspicuously in the first storey.
Numerous inscriptions in Arabic and Nagari characters in different places of the minar reveal the history of Qutb. Quwwat-ul-Islam Mosque, to the north-east of minar was built by Qutbu'd-Din Aibak in C.E.1198. It is the earliest extant mosque built by the Delhi Sultans. It consists of a rectangular courtyard enclosed by cloisters, erected with the carved columns and architectural members of 27 Hindu and Jaina temples, which were demolished by Qutbu'd-Din Aibak.
Later, a lofty arched screen was erected and the mosque was enlarged by Shamsu'd-Din Iltutmish (AD 1210-35) and Alau'd-Din Khalji. The Iron Pillar in the courtyard bears an inscription in Sanskrit in Brahmi script of fourth century C.E. according to which the pillar was set up as a Vishnudhvaja (standard of god Vishnu) on the hill known as Vishnupada in memory of a mighty king named Chandra.
The tomb of Iltutmish (AD 1211-36) was built in AD 1235. It is a plain square chamber of red sandstone, profusely carved with inscriptions. Some of the motifs viz., the wheel, tassel etc., are reminiscent of Hindu designs.
Ala'i-Darwaza, the southern gateway of the Quwwat-ul-Islam mosque was constructed by Alau'd-Din Khalji in C.E. 710 (AD 1311) as recorded in the inscriptions engraved on it. This is the first building employing Islamic principles of construction and ornamentation.