Qutb Minar is a part of a large complex comprising of many historical buildings ranging from the 12th century to the 14th century. It was declared a UNESCO heritage site in 1993. Built predominantly with red sandstone, the complex is a specimen of finest Sultanate architecture. Some of the prominent structures are: 

• Quwwatu’l-Islam-Masjid: It was Commissioned by Qutubuddin Aibak (the first ruler of the Delhi Sultanate) immediately after the capture of Delhi in 1192. He named it the Jami Masjid. It’s the earliest existing mosque in Northern India. Later, the Mosque was enlarged by two subsequent Sultans, Iltutmish who doubled its size and Alauddin Khilji who extended the enclosure of the mosque and added four gateways, one of which is the famous Alai Darwaza. 
• Qutb Minar: Its foundation was laid by Qutubddin Aibak, perhaps as a victory tower and as a Minar to call people to prayer. Aibak possibly erected just one storey, the remaining were added by Iltutmish. Both Nagari and Persian inscriptions on the Minar suggest that it was hit by lightning twice, first in the reign of Muhammad bin Tughlaq who repaired it and second, during the reign of Firuz Tughlaq who added the uppermost storey to the Minar. It has a spiral staircase of 379 steps.
• Iron Pillar: It stands in the courtyard of Quwwatu’l-Islam-Masjid. Its total height is 7.20 m. According to its Sanskrit inscription in Gupta script, it is palaeographically dated to the fourth century and believed to be constructed by Chandragupta II of the Gupta dynasty. It’s certainly brought to the complex from somewhere else as there are no other structures in the Complex from the ancient period. It is made of pure malleable iron which has not rusted till this day! 
• Iltutmish’s Tomb: Sultan Iltutmish (r.1211-36), successor of Qutubuddin Aibak, built this tomb for himself in about 1235. It’s plain from the outside but intricately carved on the entrance and interior with inscriptions written in Kufic and Naskh calligraphy. 
• Alai Darwaza: Erected in 1311 by Alauddin Khilji, it’s the massive southern gateway to the Quwwatu’l-Islam Mosque. Made with red sandstone and marble, it has arched openings on all sides and a wide but shallow dome rests atop it. Barring the north arch, rest three are in pointed horseshoe shape built on the principle of a true arch. 
• Alai Minar: It is an unfinished Minar which was initiated by Alauddin Khilji but he didn’t survive to complete it. He had intended to build it double than the size of the Qutb Minar. It has an existing height of 24.5 m. 

There are some other monuments in the complex, like the Tomb and madrasa of Alauddin Khilji and tomb of saint Imam Muhammad Ali also called Imam Zaman who came to India from Turkestan during Sikandar Lodi’s time.