A significant amount of news in recent weeks has covered the unveiling of the National September 11 Memorial on the 10th anniversary of 9/11. The Memorial Plaza, designed by architect Michael Arad and landscape architect Peter Walker, has now opened to the public. But perhaps the site’s most complex construction continues far below the plaza.

The Memorial Plaza is directly on top of a remarkable underground space: the National September 11 Memorial Museum, which is scheduled to open on September 11, 2012. With our readership of architects and designers focused on interiors, Contract is previewing this unprecedented museum—built entirely below grade—that is a challenge to design and build due to its global significance, unique site constraints, construction complexity, and the public’s expectations.

Steven Davis, FAIA, a design partner at Aedas (formerly Davis Brody Bond Aedas), has overseen the museum design (see the interview with Davis on page 80). This editor walked through the space in August with project architect Mark Wagner, an associate partner at Aedas, and saw the progress first-hand.

Visitors will enter the museum through the glass-and-steel pavilion designed by Snøhetta and completed this year. Descending via escalators or stairs to the museum itself, visitors will be oriented to the museum with an introductory exhibition as they proceed on a gently sloping ramp through the void to the bedrock level. The ramp’s walnut flooring provides a sense of warmth and familiarity in an otherwise unfamiliar space. As visitors approach bedrock level, they will see suspended aluminum-clad cubic forms demarcating the locations of the original towers.

Lighting on the aluminum will produce a sheen that is meant to evoke the ethereal nature of memories. On the ground at bedrock level—about 70 feet below the plaza—the column bases and concrete footings of the original two towers will be visible underneath the suspended aluminum walls. A 60-foot-high expanse—the original slurry wall of the site—will be intact and form the western wall of the museum.

Exhibitions will display small artifacts as well as large objects recovered from the site, including a crushed fire truck, ambulance, significant steel segments from the towers, and a portion of the iconic antenna that topped the North Tower. Thinc Design is the lead exhibition designer, with media partner Local Projects. Tom Hennes, principal of Thinc Design, describes the unparalleled exhibition design challenges. “The exhibits must accommodate an unusually wide range of needs and expectations that will strongly shape visitors’ experiences,” Hennes says. “We have had to plan the exhibits in such a way that people are able to easily and intuitively seek out what is most important to them, including those things most important for a particular person or family to avoid.”

Wagner had a role at the site in the days after 9/11 overseeing the artifact recovery program, and has been on site nearly daily as project architect of the museum. He acknowledges it’s not just any architectural project. “To me, the importance is its personal and emotional signifi-cance,” Wagner says. “By providing access to the authentic site and the recovered artifacts, we hope that the museum will allow people to experience the site on their own terms, with their own memories, and provide the appropriate platform to retell the facts to our future generations.”