Iron Pillar at Qutb Complex of Delhi is one of the most interesting structure other than Qutb Minar. This is 7.3 m tall of which one meter is below the ground. It is at the foot 48 cms in diameter and 29 cms tapering at the top. The pillar weighs approximately 6.5 tonnes.
This pillar dates back to 4th century A.D. The pillar is made of 98% of pure iron. In-spite of such high proportion of iron, it is 100% corrosion resistant even after 1600 years. This feat clearly shows great technological achievements of the ancient Indians.
There are Sanskrit inscription in the Brahmi script on the pillar that states it was erected as a flagstaff in honor of the Hindu god, Vishnu, and in the memory of the Gupta King Chandragupta II. It is not clear how and when the pillar has been moved from Udaygiri to its present location.