Fought over, stalled, reconceived, and finally built, the National September 11 Memorial Museum has followed a tortuous path since it was first proposed in Daniel Libeskind’s 2003 master plan for Ground Zero. While nearly every part of the redevelopment effort at the World Trade Center site in lower Manhattan has generated debate, the museum has been a lightning rod for particularly intense criticism and controversy. Its role as the main keeper and shaper of the 9/11 narrative made such struggles inevitable, since so many different groups were affected by the 2001 attacks: those who died and their families, people who witnessed the horrifying events, residents of lower Manhattan, businesses in the area, and citizens of the city, the nation, even the world. On September 12, we were all New Yorkers and we all had our own particular connection to the events of the day before.

The museum opens to the public on May 21, but President Obama and First Lady Michelle Obama will dedicate it on May 15 at the start of a six-day period of visits by 9/11 survivors, relatives of victims, rescue workers, and Lower Manhattan residents.

Just as the range of “stakeholders” in the museum seemed limitless, the number of agencies with at least some control over it was mind-boggling: the City of New York, the State of New York, the Port Authority of New York and New Jersey, the Lower Manhattan Development Commission (LMDC). Even the official client for the project kept changing, starting with the LMDC, then moving to the World Trade Center Memorial Foundation, which morphed into the National September 11 Memorial & Museum.

Although designed by different architects, the museum and the memorial have a symbiotic relationship with the first occupying the underground space below the latter. Any change in one inevitably affected the other. Work on the memorial started first with the selection in January 2004 of a scheme entitled Reflecting Absence by architect Michael Arad and landscape architect Peter Walker. That project called for a street-level memorial plaza connecting deeply recessed pools in the footprints of the destroyed Twin Towers; it opened on the 10th anniversary of the attacks.

The architect for the museum, Davis Brody Bond (DBB), knew from the start it would be designing an underground facility. But how visitors would get down there was unclear for several years. In his original scheme for the memorial, Arad envisioned a set of galleries around the bases of the two pools—underground spaces where people would view the names of those killed on 9/11 through sheets of cascading water. Security concerns forced him to move the name plaques to the plaza level and eliminate the below-grade galleries. Meanwhile, Snøhetta was picked to design a cultural building that would include the International Freedom Center and the Drawing Center. For different reasons, both of those organizations dropped out of the project, leaving the Snøhetta building without a purpose. Eventually, a downsized version of that building became the entry pavilion for the museum.

Rising costs threatened the museum at several moments during its planning and development. By the end of 2011, with the price tag for the museum nearing $1 billion, construction was halted. Allocating costs for any one piece of the redevelopment of Ground Zero, though, is a murky business, since the infrastructure that runs through the entire site is so complicated, expensive, and interwoven with everything else. According to the National September 11 Memorial & Museum, the cost of building the eight-acre memorial and the 110,000-square-foot museum came to $700 million.

Located on the site of the events it commemorates, the 9/11 museum encompasses physical remnants of the original World Trade Center—most important being the footprints of the Twin Towers and the now-famous slurry wall, the massive retaining structure that protected the site from the waters of the Hudson River and held strong during the long process of removing the rubble of the destroyed buildings. “Where most museums are buildings that house artifacts, this museum has been built within an artifact,” says Alice Greenwald, the director of the museum.

The museum entry pavilion sits between the two pools of the memorial, an angular, steel-and-concrete structure clad with stainless-steel panels and glass. From the plaza, you can look inside in places or see yourself in the metal skin with the new 1 WTC Tower rising behind you. “The pavilion reflects the people who are alive now, bridging the future and the past,” says Craig Dykers, the Snøhetta partner in charge of the project. Visitors enter from the northeast, close to Santiago Calatrava’s transportation center, whose expressionistic steel structure is visible now but still under construction. Inside, the pavilion welcomes visitors with a light-filled space dressed with warm ash floors and ceilings. A wood stair takes you up a flight to a 165-seat auditorium and a room reserved for relatives of 9/11 victims that offers a place to look out over the memorial.

From the entry level of the pavilion, visitors start their journey down to the museum proper by taking a broad stair sheltered on two sides and above with large panes of glass. Rising up through this bright space, two steel columns or tridents from one of the destroyed Twin Towers stand as powerful reminders of what happened on 9/11 and important guideposts for the procession that is about to begin.

Easing the transition from Snøhetta’s shimmering pavilion to the underground spaces of the museum was a critical task for the architects at Davis Brody Bond. As you descend to the first level below ground, you feel the presence of the plaza slip away as daylight becomes weaker and the wood stairs turn from light ash to dark wenge. One flight down, you reach a broad space with an information desk in front of you and high balustrades on either side, which dip down then up in a V shape to offer views to spaces below. You’re not quite sure what you’re looking at: a pair of large rectangular volumes clad in recycled aluminum with a mottled surface that softly diffuses the light. You see only parts of each volume, so they remain a mystery. Later you will learn these are the bottoms of the memorial pools occupying the spaces where the Twin Towers had stood.

“We used a strategy of progressive disclosure,” says Steve Davis, the DBB partner in charge of the project. “We knew we needed to give visitors the time and space to slowly acclimate to the experience of this museum,” he explains. So he and his team created a long “ribbon” of ramps, stairs, and overlooks that take people down the 70 feet from the plaza to bedrock. From one landing, you see the enormous West Chamber, one of the largest ceremonial spaces in New York City, and you finally grasp what those aluminum-clad volumes are and what had been there before. You also get your first look at the slurry wall, which had been built four decades ago as a prosaic piece of infrastructure but now stands as a symbol of resilience. Like the Western Wall in Jerusalem, this one is the foundation or mount of something important that has been lost.

As you move down to the exhibition level at bedrock, you encounter almost nothing didactic, nothing that explains. Near the top, on the level with the information desk, you see a large map of the northeast of the United States with flight paths of the planes that struck in New York, Washington, and Pennsylvania on one wall. Further along you see photographs of people witnessing the tragedy of 9/11, their faces projected onto freestanding vertical panels and you hear voices of people remembering what happened. As you continue down the circulation ribbon, you find some large objects—twisted pieces of steel that at first look more like John Chamberlain sculptures than artifacts of destruction.

Instead of wall labels or blocks of text, the route down to the exhibition level offers raw space and an experiential procession from daylight to bedrock. “We wanted to create a sense of void as a metaphor for the enormity of our loss,” says Carl Krebs, a DBB partner. Krebs says he remembers walking down the long construction ramp that trucks used to haul out the debris of the destroyed towers and feeling a pinch in his chest every time he made the descent to select artifacts to be preserved for the museum. “We wanted to allude to that experience here, but not recreate it in any literal way.”

On the lowest level, you find more artifacts—a crushed fire truck from Ladder 3, a piece of the antenna that had topped the North Tower, and the so-called Last Column, the 37-foot tall steel member that was the last object removed from the site and is now covered with graffiti from the rescue companies that worked there: PAPD 37, NYPD 23, FDNY 343, and more. The remnants of 73 column bases surround the two footprints of the lost towers, marking the rhythm of Minoru Yamasaki’s soaring structure. Inside the footprints, visitors find the two main exhibitions—one devoted to remembering the nearly 3,000 people who died on 9/11 and the six people killed in the bombing of the WTC in 1993 and the other a historical examination of the events of 9/11, what led to them, and what has happened afterward. [Note: When this writer toured the museum on May 12, the two main exhibitions were not yet open.]

“There is no established museum voice here,” says Tom Hennes, the principal of Thinc Design, which designed the exhibitions. “There are lots of different voices, which we tried to capture in many different ways.” Hennes and his team used a dual strategy in dealing with all the material displayed in the museum. “The physical artifacts on display are the ‘here and now,’ while the enormous quantity of digital material that record the event represent the ‘there and then.’” Thinc worked with Local Projects, a media firm, to present the digital documentation of the events and their aftermath. Their basic strategy was to move visitors incrementally from the larger experience of 9/11 to more intimate and emotional moments. For example, in the memorial exhibition, visitors first see walls covered with photographs of all the victims, then go to an inner chamber where one victim at a time is presented in images, words, and audio. In the historical exhibition, progressively more traumatic displays are placed further inside, so a visitor may decide at one point or another, not to go any further. Before reaching still photographs of people jumping from the burning towers, visitors see a warning about the material that will be presented.

Because so many of the people who will visit this museum bring with them their own memories of 9/11, the architects and designers faced the challenge of not doing too much. By leaving enough space here for each visitor to fill with his or her own feelings and experiences, the design team has allowed the place to feel very much alive, a remarkable feat for an institution dedicated to remembering an event that began with destruction.