Tim Maly takes us on a tour of New York City's landscapes of dredge, and explores how the city's past, present and future are shaped by technologies and processes of what he calls "the greatest unrecognized landscape architecture project in the world."

Steve Duncan -- historian, photographer and explorer -- reflects on wastewater infrastructure, underground rivers, and the thrills and urban lessons he's discovered beneath the surface of cities.

Dana Gumb explains how the City has engineered Staten Island's wetlands and waterways to enhance their natural ability to convey, store and filter stormwater.

Architects Jenny Broutin and Carmen Trudell reflect on the development of their prototype for energy generating revolving doors, offering a case study for other innovators.