Kelly takes a virtual trip back in time to see what Manhattan looked like 400 years ago before the tops of hills were scraped off and dumped into the river. Kelly also journeys through underground brooks and streams, and we learn what's really underfoot at South Street Seaport where the skeletons of sunken ships provided the City's earliest landfill. Kelly then explores how landfill changed two centuries later with the engineering marvel that created the Twin Towers of the World Trade Center.