What made you zero in on Calcutta as the subject of this book?
When I was new to National Geographic Magazine in May 1972, I did the rounds of various departments before starting on a career as a staff photographer. In the summer, I helped edit the work of two photographers working on a story about Calcutta. I was in on the final layout and design, agonising over images, accuracy, balance, and finding a way of telling a story about Calcutta that would have some lasting benefit for history. So, I caught the bug early in 1972. As an adult, I have read many books about Calcutta, from the works of Kipling to American author Paul Theroux.u00a0I also have many Bengali friends and colleagues who hail from Calcutta.

Built with 121 massive steel cables, the Vidyasagar Setu connects Calcutta with its sister city Howrah. It is the longest cable-stayed bridge in India and one of the 50 longest in the world.