Hundreds of people who came face to face with the horror of 9/11 are now serving as volunteer tour guides at the rebuilt World Trade Center complex in New York.
One is a woman who walked through down 82 flights of stairs to escape the burning north tower.
Another guide is a retired doctor who lost his son, an equity trader for Cantor Fitzgerald. He takes a train from Washington each month to lead tours.
The tours are organized by the 9/11 Tribute Center, a nonprofit that presents the attacks and the aftermath as journeys of survival.
The center has trained about 800 guides who were survivors, first responders, victims' family members and lower Manhattan residents.
Some guides say recounting their stories has helped with their emotional recovery.