Iron pillar of Chandragupta II Vikramaditya (375–414 CE) (Delhi)

 pillar, scheduled ancient monument

The iron pillar is one of the world’s foremost metallurgical curiosities. The pillar, almost seven metres high and weighing more than six tonnes, was erected by Chandragupta II Vikramaditya (375–414 CE), (interpretation based on careful analysis of archer type Gupta gold coins) of the Gupta dynasty that ruled northern India 320–540.

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The pillar, with an idol of Garuda at the top, was originally located at a place called Vishnupadagiri (meaning “Vishnu-footprint-hill”), identified as modern Udayagiri, situated in the close vicinity of Besnagar, Vidisha and Sanchi, towns located about 50 kilometres east of Bhopal, in central India. Vishnupadagiri is located on the Tropic of Cancer and, therefore, was a centre of astronomical studies during the Gupta period. The Iron Pillar served an important astronomical function, in its original site; its early morning shadow fell in the direction of the foot of Anantasayain Vishnu (in one of the panels at Udayagiri) only in the time around summer solstice (June 21). The creation and development of the Udayagiri site appears to have been clearly guided by a highly developed astronomical knowledge. Therefore, the Udayagiri site, in general, and the Iron Pillar location in particular, provide firm evidence for the astronomical knowledge in India around 400 CE.

It is the only piece of the Jain temple remaining, which stood there before being destroyed by Qutb-ud-din Aybak to build the Qutub Minar and Quwwat-ul-Islam mosque. Qutub built around it when he constructed the mosque.

The pillar bears an inscription which states that it was erected as a flagstaff in honour of the Hindu god, Vishnu, and in the memory of the Gupta King Chandragupta II (375–413). Made up of 98% wrought iron of pure quality, it is 23 feet 8 inches (7.21 m) high and has a diameter of 16 inches (0.41 m). Also, it was confirmed that the temperatures required to form such kind of pillars cannot be achieved by combustion of coal. The pillar is a testament to the high level of skill achieved by ancient Indian iron smiths in the extraction and processing of iron.

It has attracted the attention of archaeologists and metallurgists as it has withstood corrosion for the last 1600 years, despite harsh weather. Its unusually good corrosion resistance appears to be due to a high phosphorus content, which together with favorable local weather conditions promotes the formation of a solid protective passivation layer of iron oxides and phosphates, rather than the non-protective, cracked rust layer that develops on most ironwork.

A fence was erected around the pillar due to the popularity of a tradition that considered it good luck if you could stand with your back to the pillar and make your hands meet behind it.