PURIFICATION: Water from the Hudson is drawn to the top of Pedersen's tower, purified, and released along a promenade to the bay below.

William Pedersen proposes a continuous rooftop memorial promenade starting at the Statue of Liberty ferry landing and rising steadily above new residential blocks and office buildings. The sky promenade forms a populous wall spiraling around the original World Trade Center site that culminates in a 2,001-foot tower overlooking the footprints of the original towers, which will be transformed into reflecting pools. The upper reaches of the tower itself will be equipped with banks of wind turbines and solar panels, and the sky-memorial promenade will have a stream of Hudson River water purified and filtered as it courses down to the harbor, serving the building along the way and, at least symbolically, cleansing the site. The wall of buildings is broken by the surrounding street grid into segments, each created by different design teams. The scheme accommodates 10 million square feet for offices, apartments, stores, and cultural institutions, including a memorial museum. Pedersen, whose firm has built extensively in New York and abroad, including projects that are among the tallest in the world, compares the sky promenade to the exhilarating experience of walking on the pedestrian decks of New York's suspension bridges.

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