Iron Pillar

The iron pillar of Delhi is a structure 7.21 metres high with a 41-centimetre diameter that was constructed by Chandragupta II, and now stands in the Qutub complex at Mehrauli in Delhi, India. The metals used in its construction have a rust-resistant composition. The pillar weighs more than six tonnes and is thought to have been erected elsewhere, perhaps outside the Udayagiri Caves, and moved to its present location by Anangpal Tomar in the 11th century.

Source: Wikipedia