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Photo: Nvvchar, CC BY-SA 3.0 via Wikimedia Commons
It was originally the tomb of Quli Khan who was the brother of Adham Khan and in turn foster brother of Akbar. Later Sir Thomas Metcalfe (who was a negotiator between Mughal Empire and the British East India Company) bought the structure remodelled it, and became one of the two Metcalfe Houses also known as Dilkusha. It is in ruins as it was highly vandalized during the Revolt of 1857.
Metcalfe House is the name given to two residential houses built in the 19th century in Delhi; one is near Old Delhi Civil Lines and the other is in Mehrauli, South Delhi. These were built by Sir Thomas Metcalfe (1795–1853), a civil servant, when he was the Governor General's last British resident (agent) at the Mughal court of Emperor Bahadur Shah Zafar.
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Smith's Folly, which once stood on top of the Qutb Minar, has been removed and put on the southeastern corner of the Qutb complex.
A marble sundial
this octagonal tomb commemorates a Turkestani iman who was based in the mosque during the reign of Sikandar Lodi.
Alai Darwaza
This square, domed building once acted as the entrance to the mosque but is now tucked away behind the minar. Inlaid marble decorations and latticed stone screens.
क़ुत्ब मीनार / قطب منار Qutb Mīnār
The most famous structure on the grounds is the Minar itself. At 73m tall, it is the second tallest minar in India (after Fateh Burj in Mohali), and was the tallest "skyscraper" in the world when built (1193-1368). It is often visible from the air when flying into IGI airport. It was constructed on the orders of Qutb-ud-din Aybak, founder of the Slave Dynasty, and named after him. Delicately carved and inscribed with Arabic inscriptions, its red sandstone and marble have been astonishingly well-preserved, and it is still an awe-inspiring sight today. The top of the tower has twice been rebuilt after an earthquake, and the base has been restored more recently. While entry into the tower itself is no longer permitted, for ₹10 per 5 min you can view the scenery via a little webcam on top.
In the centre of the mosque. True to its name, this is a 7 m iron pillar erected in 400 AD by Chandragupta II Vikramaditya, also known as "he, by the breezes of whose prowess the southern ocean is even still perfumed" according to the inscription carved on the base. Alas, Chandragupta II's perfume has long since faded, but to the amazement of metallurgists everywhere, his pillar is still going strong, after 1,600 years. The corrosion resistance results from a layer of crystalline iron hydrogen phosphate forming on the high phosphorus content iron, which protects it from the effects of the local Delhi climate. The pillar is 7.21 m high, 1.12 m of which is below ground. The base rests on a grid of iron bars soldered with lead into the upper layer of the dressed stone pavement. It is estimated to weigh more than six tonnes.