“During his four years of research, he walked almost every day. “I did it in the morning. I did it in the evening. I did it on the weekends. I did it in the rain, in the snow, in the summer. It came to about thirty-five, forty miles a week, a hundred twenty a month, fifteen hundred a year.” He has a near-photographic memory, and can envision with ease landmarks and parks, the shapes of buildings, the curves of streets.”

From: A Walker in the City