The Iron Pillar of Delhi stands in the courtyard of the Quwwat ul-Islam Mosque within the Qutb Minar complex, and is one of the world's most remarkable metallurgical achievements. Constructed in the 4th or early 5th century CE during the Gupta period, this 7.2-metre-high pillar of 98% pure iron has survived 1,600 years of the Delhi monsoon with almost no corrosion — a feat that still puzzles modern materials scientists.
The pillar was originally erected elsewhere (possibly Udayagiri in Madhya Pradesh) and brought to Delhi during the construction of the mosque. A Sanskrit inscription on the pillar praises a king named Chandra, likely Chandragupta II. A popular tradition once held that wrapping your arms around it from behind and clasping your hands would bring good luck — the pillar is now fenced to prevent contact.