India, June 19 -- Delhi has always been a city of bridges. It has 17 major ones across the Yamuna, an eighteenth is almost ready, and it has just approved two more. They are critical to a third of the city's population that lives on the other side of the river. Before 1857, Delhi was approached either by river or from Ghaziabad across a floating "bridge of boats" that stretched over the Yamuna near the Red Fort and Salimgarh Fort. Early travellers wrote of the dramatic first glimpse of Shahjahanabad's minarets rising above the river as they crossed into the city.

The arrival of the iron railway bridge, or Loha Pul, in 1866 transformed that experience. As Delhi linked to Calcutta and the expanding railway network, visitors arrived through...