In the courtyard of the Quwwatu`l-Islam mosque stands the famous iron pillar, which bears a Sanskrit inscription in Gupta script, palaeographically assigned to the 4th century, a date confirmed by the peculiar style of its `Amalaka`-capital.

The inscription records that the pillar was set up as a standard or dhvaja of god Vishnu on the hill known as `Vishnupada`, in the memory of a mighty king, named `Chandra`, who is now regarded as identical with Chandragupta II (375-413) of the imperial Gupta dynasty. A deep hole on the top of the pillar indicates that an additional member, perhaps an image of `Garuda`, was fitted into it to answer to its description as a standard of Vishnu.

The pillar was brought from somewhere, else, as no other relics of the 4th century are found at the site. There is a strong bardic tradition that it was brought here - wherefrom, nobody knows - by Anangpal, Tomar king credited with the founding of Delhi. The base of the pillar is knobby, with small pieces of iron tying it to its foundations, and a lead sheet covers the portion concealed below the present floor-level. The total length of this slightly tapering shaft is 7.20m, of which 93cm is buried below the ground. The metal of the pillar has been found to be almost pure malleable iron. Its portion below the ground shows some signs of rusting, but at a very slow rate. The manufacture of such a massive iron pillar, which has not deteriorated much during sixteen hundred years of its existence, is a standing testimony to the metallurgical skill of ancient Indians.