More than twelve years after al Qaeda attacked the United States, a museum dedicated to that horrific moment is set to open on Thursday with an appearance by President Barack Obama and a small group of survivors, rescue workers and family members of the victims.
"We will not forget what happened in this place," Joe Daniels, president of the foundation that built the museum, told ABC News Anchor David Muir during a walk through the exhibits before it opens. "Our visitors will come from outside, where the memorial is, come into the museum and then proceed really on a journey."
The journey takes the visitor down long stairwells to the subterranean realm of Manhattan, to the very bedrock that once supported the Twin Towers. Almost immediately, you are confronted with powerful sights: the clear sky on the morning of the attacks, a steel beam curved where it was hit by a jet's nose, the "Survivor Stairs" that helped hundreds escape the World Trade Center complex and delivered them to safety on 9/11.
Once inside, they're offered a variety of ways to relive that somber day and reflect on the victims and survivors:
Guests are encouraged to visit the interactive museum's "Reflecting on 9/11" exhibit, where they can record their own thoughts that will be included in the permanent collection and played alongside those of victims, survivors, family members and world leaders.
Each of the victims of the attacks is remembered in the "In Memoriam" section, where photos of the deceased line the walls. In the exhibit, visitors can use an interactive console to select and listen to spoken remembrances of their loved ones.
The shoes worn that day by Florence Jones are on display. Soon after the second plane hit, she removed them so she would be able to run down quickly from the 77th floor and to safety.
In the space dedicated to United Flight 93, which crashed in Shanksville, Penn., there is a display with the watch worn by Todd Beamer, one of the heroes whose "let's roll" inspired the uprising that kept terrorists from flying that jet to Washington, D.C.
There is an area dedicated to those who were killed and injured in the 1993 blast at the World Trade Center, the first effort by terrorists to destroy the Twin Towers.
The most controversial section of the museum is the exhibit that explains the rise of radical Islam that gave birth to al Qaeda. Curators believe that visitors need that kind information to understand 9/11, though some have suggested the displays and explanatory film cast all Muslims in a poor light. And located next to that section is the exhibit that displays the faces of the 19 hijackers. Some questioned whether that was glorifying villains and suggested it would be hurtful to survivors, but organizers said it was necessary if the actual events were to be portrayed accurately and completely.