Correct Answer: (4) Delhi
Solution:The Iron pillar of Delhi is 23 feet 8 inches high (7.2 metres) with 16 inches diameter structure, was constr ucted by a 'King Chandra', Probably Chandra g upta II, and is currently standing in the Qutb complex at Mehrauli in Delhi. It is famous for the rust resistant composition of the metals used in its construction.