As an urban historian and photographer Steve Duncan tries to peel back the layers of a city to see what's underneath.
From the tops of bridges to the depths of sewer tunnels, these explorations of the urban environment help him puzzle together the interconnected, multi-dimensional history and complexity of the great metropolises of the world.
Erling Kagge, a 47-year-old Norwegian adventurer, had ascended Mount Everest and trekked on foot to both the North and South poles.
The two of them forged a new frontier: an extended exploration of the subterranean city, during which they lived inside the subsurface infrastructure, sleeping on the trail, as it were.
"The opportunity to see New York in a way no one else has, from the inside out, is, for me, as inspiring as walking to the poles and climbing Everest," - Mr. Kagge.