The Survivor Tree is the first tree to bloom each spring. A charred Callery pear tree that was rescued from Ground Zero, it was nursed back to health and returned to the site in 2010.

Once the decision was made to locate the names above ground, the issue of placing individual names remained. Arad had proposed in 2004 that they be arranged randomly around the pools, which would reflect the haphazard brutality of the attacks, but the families of the victims and first responders expressed their dissatisfaction with that approach in hundreds of letters. Ordering the names chronologically did not make sense, and alphabetizing them would have had the heartless anonymity of a phone book. Compounded by grief, the controversy over the names roiled on.

Bloomberg called Arad into his office to find a solution. What emerged was the idea to arrange the names in nine broad groups that would reflect the victims’ geographic locations on September 11. At that point, Arad began to explore placing the names next to each other in meaningful ways within the nine groups. In June 2009, the 9/11 Memorial staff asked the victims’ families for their input on their loved ones’ affiliations and name placement on the memorial; all requests, more than a thousand, were honored. “It was a very emotionally charged and difficult period of time for the people involved in it. We were able to meet every adjacency request and enrich the meaning of the memorial profoundly. It doesn’t visually change anything, but it emotionally changes it,” Arad said. “It’s a way to take a personal story of loss and convey it and transmit it in a very direct way that, in my mind, fights the abstraction of close to 3,000 dead.”

When I asked Arad what the long process of bringing the memorial into being taught him, he paused. Finally, he said, “The fact that I’m taking some time to respond to that question is probably one of the ways that the project has changed me.” It was a wry yet poignant observation from someone who was thrown into an arena of professionals who had far more experience than he did and who made sure he knew it. Yet, much like his advocate Maya Lin, whose strong opinions three decades ago decided the form of the Vietnam Veterans Memorial, he believed he had a moral obligation to see the memorial through as he envisioned it. And then he devoted a quarter of his lifetime to its realization. “I was very young, very idealistic. I don’t think I could have done this any other way, without a dose of naïveté and belief that we will get this right. Seeing it from the other side, it seems like such a narrow path that we traversed as a group, and we easily could have slipped off the side of this path into something altogether different. Having a clear idea guiding the design was key.” Throughout, he held on to two critical ideas: “Making absence visible and making it a public and civic space.… That public realm allowed us to come together and respond stoically and in measured fashion, but at the same time with compassion and feeling. That was always important to me and had to be part of how we thought about the site.”

THE PAVILION

Approaching the memorial plaza, one sees a small wedge of a building glistening above the treetops. From some vantage points, it appears to spring from the ground; from others, it bows before the 9/11 Memorial. Designed to lead the eye and pique curiosity, the crystalline wedge, known as the Pavilion, attracted visitors even before its 2014 opening, thanks to its unique shape and reflective façade. The three-level structure serves as the entrance to the subterranean 9/11 Memorial Museum and also as a navigational guide, funneling visitors toward the space between the two memorial pools. The sole building on the plaza, it was designed by Snøhetta, an architectural firm founded by Kjetil Trædal Thorsen and Craig Dykers, the project’s executive architect.

Dan Euser Waterarchitecture engineered the ingenious fountains. In his backyard, just north of Toronto, Euser built a full-scale mockup of a forty-foot (12.2 m) section of one of the pools in order to study the water’s performance, and then developed an elegant rounded weir along the lower part of the parapet. The weir’s serrated metal edges channel the water into cascading streams.