Even before the design competition was announced, National 9/11 Memorial designer Michael Arad sketched out his first idea for a memorial design: two square voids floating in the Hudson River.

Arad also wanted to make the memorial plaza a place where people could gather, much like Washington Square Park (above), where New Yorkers gathered in the days following the attacks. Arad was among them: "They were places that we gathered so that we would not be alone in the face of that attack," he remembers, "so that we could find meaning in the company of others, in trying to confront the brutality of that day. … I felt a tremendous sense of kinship."

A rendering of an aerial view of the The National September 11 Memorial Plaza. Arad ultimately incorporated both ideas — twin square voids and a gathering space — in his final design.

Studio 360 host Kurt Andersen and Arad walk towards the South Pool.

While waterfalls will eventually flow 24 hours a day at each pool, the South Pool was dry on one of the days we visited. The pool's massive scale is more obvious when you spot the neon-vested workers in the far corner of the floor. Panels (seen in foreground) engraved with the names of victims outline both pools.

View of the south pool with the 9/11 Memorial Museum on the north side (right). The shiny glass-clad pavilion which serves as an entrance to the museum building sits between the north and south pools. The trees immediately surrounding the pool create a kind of envelope, Arad says, marking the actual border of each tower's footprint.

A view of the North Pool looking west toward the World Financial Center's glass atrium, Winter Garden. The waterfalls have a 30-foot drop.

A view of the North Pool looking east. The cranes on the construction site for the new transit hub border the east side of the memorial. The trees extend into a formal grove on the plaza — 400 oak trees are part of the Memorial Plaza's design.

(left to right) Studio 360 engineer Josh Rogosin, memorial architect Michael Arad, and Kurt Andersen look at a corner name panel on the edge of the North Pool.

A view of the construction site that borders the south side of the Memorial Plaza. Because there is so much construction on all sides of the memorial, it will be years before it is fully stitched into the city's everyday life, as Arad hopes.