Now, to an emotional milestone for the nation. Tomorrow, the memorial and museum, honoring the victims of the September 11th attacks will be dedicated in downtown Manhattan. ABC's David Muir is there... See More
Now, to an emotional milestone for the nation. Tomorrow, the memorial and museum, honoring the victims of the September 11th attacks will be dedicated in downtown Manhattan. ABC's David Muir is there at ground zero for us this morning. Good morning, David. Reporter: Robin, great to see you. As you know, this was a decade in the making. And to give everyone at home an idea of where we are, ground zero, of course. This is the soaring new world trade center behind me. A magnificent sight. But we're here for the museum, for a moving tour that we're taking inside that building. You go down seven stories below, down to the original bedrock on which the twin towers once stood. And I was struck immediately by the voices. This was "Good morning America" shortly after the first plane hit that morning. There's been some sort of explosion at the world trade center in -- Obviously, a major fire there. And -- Reporter: That confusion, before we all knew, relieved in this museum. The first thing you hear when you walk in, the voices. September 11th. On September 11th. Reporter: Americans remembering where they were. Their own words lighting the way. We were in a meeting when someone barged in and said -- Reporter: On the first walls, the map. It shows the flights the moment they turn when the hijackers take control. As you walk through the museum, beside us right there. The survivor stairs. Hundreds of people used this staircase as an escape route on 9/11, when the attacks were taking place. Running down the stairs to safety was a lifeline. Reporter: Those stairs weigh 58 tons. The entire museum built around them. Around the corner, big red, the fire truck, ladder 3. So many remember that brave captain. I'm on the 35th floor. Relay to command post, we're trying to get up. Reporter: Captain brown and ten of his men, lost. Here in the museum, they remember all of the planes. These were parts from flight 77, pulled from the Pentagon. This clock frozen at 9:37. A melted rolodex and someone's phone. It was Todd beemers, one of the heroes that took back that flight. And on his watch, the date. The 11th. And Florence Jones, too, who barely escaped the south tower. She took off her shoes. One of the last to get out. She's given them to the museum. And we found a message of hope, even from that awful day. A nasa commander saw the smoke and listened to what he said. I know it's difficult for everybody in America right now. The country still looks good. And for new yorkers, your city still looks great from up here. Reporter: The message from space. The president will be here tomorrow to dedicate the museum, robin. And I have to tell you, it is a powerful walk through this new site, honoring those that were lost. And of course, all of the first responders who did, in fact, save so many that morning. Well said, David. Well said. Thank you. And we will be covering the president's speech tomorrow.
This transcript has been automatically generated and may not be 100% accurate.