While the ancients recognised the wonders of iron, it was mostly used to make household vessels, jewellery and weapons, because the iron they extracted was too soft to build with, and they didn’t know how to strengthen it enough to create an entire building or bridge. There are nonetheless rare examples of structures that use it: in A Record of Buddhistic Kingdoms, the Chinese monk Fa Hsien wrote about suspension bridges held up by iron-link chains in India around the time the pillar in Delhi was made.
