Designed by Michael Arad and Peter Walker, the Reflecting Absence memorial consists of two voids on the sites of the twin towers' footprints. Surrounded by a forest of trees and lawn, each void will feature rings of cascading water falling into illuminated reflecting pools.
Adjacent to the two pools, a memorial museum will extend 100,000 square feet underground and will use artifacts and exhibits to tell the story of September 11, 2001, and February 26, 1993. Visitors also will be able to view a section of the massive slurry wall that held back the Hudson River during the attacks.
More than 400 sweetgum and swamp white oak trees will be planted in the Memorial plaza. They were chosen partly because each fall around 9/11 they will turn an array of colors -- the oaks turn amber, golden brown and pink; the sweetgums turn orange with some red, purple and gold. The Callery Pear tree -- the only surviving tree from the original WTC site -- was replanted on the Memorial Plaza in December 2010.
View a 3D model of the site: http://blog.national911memorial.org