The iron pillar at Qutub Minar, standing 7.2 meters tall, has impressively remained rust-free for 1600 years, a feat attributed to its unique composition and ancient craftsmanship. Located in New Delhi, this UNESCO World Heritage site showcases the remarkable durability of wrought iron. Researchers from the Indian Institute of Technology (IIT) Kanpur uncovered the reasons behind its enduring condition. They found that the pillar contains high levels of phosphorus, which is absent in modern iron, along with low levels of sulphur and magnesium. The artisans employed a method called forge welding, where they heated and hammered the iron, maintaining its phosphorus content. Additionally, a protective layer known as misawite, comprised of iron, oxygen, and hydrogen, forms on the surface under specific environmental conditions, further enhancing its corrosion resistance. This combination of high phosphorus content and traditional techniques has allowed the pillar to withstand the elements and remain a testament to ancient engineering.