New Delhi’s Iron Pillar has long fascinated scientists both at home and abroad. But it wasn’t until 2003 that experts cracked the metallurgical mystery behind this unusual attraction.

The origin of the remarkable Iron Pillar, part of the world-heritage-listed Qutub funerary complex in India’s Delhi, is lost to time. All sorts of ideas have been put forward over the decades.

Standing rust-free for over 1,600 years, Delhi's Iron Pillar defies time and science. Its ancient phosphorus-rich alloy holds secrets modern metallurgy still can't crack.