Qutub-Minar in red and buff standstone is the highest tower in India. It has a diameter of 14.32m at the base and about 2.75m on the top with a height of 72.5m.
Qutb-u'd-Din Aibak laid the foundation of Qutab Minar in AD 1199. The minar was said to have been built to celebrate the victory of Mohammed Ghori, the invader from Afghanistan, over the Rajputs in 1192. He raised the first storey, to which were added three more storeys by his successor and son-in-law, Shamsu'd-Din IItutmish (AD 1211-36). All the storeys are surrounded by a projected balcony encircling the Minar and supported by stone brackets, which are decorated with honeycomb 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. According to the inscriptions on its surface it was repaired by Firoz Shah Tughlaq (AD 1351-88) and Sikandar Lodi (AD 1489-1517).
Quwwat-ul-Islam Mosque, to the northeast of Minar was built by Qutbu'd-Din Aibak in AD 1198. It is the earliest 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 Jain temples, which were demolished by Qutbu'd-Din Aibak as recorded in his inscription on the main eastern entrance.
Later, a lofty arched screen was erected and the mosque was enlarged, by Shamsu'd- Din IItutmish (AD 1210-35) and Alau'd-Din Khalji. The Iron Pillar in the courtyard bears an inscription in Sanskrit in Brahmi script of 4th century AD, according to which the pillar was set up as a Vishnudhvaja (standard of Lord Vishnu) on the hill known as Vishnupada in memory of a mighty king named Chandra. A deep socket on the top of the ornate capital indicates that probably an image of Garuda was fixed into it.
The Tomb of IItutmish (AD 1211-36) was built in AD 1235. It is a plain square chamber of red sandstone, profusely carved with inscriptions, geometrical and arabesque patterns in Saracenic tradition on the entrances and the whole of interior. 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 AH 710 (AD 1311) as recorded in the inscriptions engraved on it. This is the first building employing Islamic principles of construction and ornamentation.
Alau'd-Din Khalji commenced Ala'i Minar, which stands to the north of Kutub-Minar, with the intention of making it twice the size of earlier Minar. He could complete only the first storey, which now has an extant height of 25 m. The other remains in the Qutab complex comprise Madrasa, graves, tombs, mosque and architectural members.