<P> The iron pillar of Delhi is a 7 m (23 ft) kirti stambha (column of fame or victory column), originally erected and dedicated as dhvaja (banner) to Hindu deity lord Vishnu in 3rd to 4th century CE by king Chandragupta II, currently standing in the Qutb complex at Mehrauli in Delhi, India . It is famous for the rust - resistant composition of the metals used in its construction . </P> <P> The pillar has attracted the attention of archaeologists and materials scientists because of its high resistance to corrosion and has been called a "testimony to the high level of skill achieved by the ancient Indian iron smiths in the extraction and processing of iron ." The corrosion resistance results from an even layer of crystalline iron hydrogen phosphate hydrate forming on the high - phosphorus - content iron, which serves to protect it from the effects of the Delhi climate . </P>

What is the mehrauli pillar in the complex of qutub minar primarily famous for