The World Trade Center was the first target of the terror plot.
On a clear morning five years ago, a hijacked plane rammed into a office building that seemed to reach into the sky. A short time later, another jet flew into an adjacent twin tower.
The world looked on in horror as these two New York City landmarks collapsed - filling the streets with the grayish powder of crumbled concrete and twisted chunks of metal.
Some call the site "holy ground." But most Americans simply refer to it as "ground zero."
It was there that President Bush began 24 hours of events marking the fifth anniversary of the September 11th attacks, laying memorial wreaths in two dark reflecting pools where the towers once stood.
Not a word was said. The only sound came from bagpipers nearby who played a mournful version of "America The Beautiful" as the president and Mrs. Bush moved from one reflecting pool to the other.
The notes could be heard, though faintly, at a nearby church, where emergency workers and volunteers found a place of refuge during the 9/11 rescue effort. In a pew where the first president of the United States - George Washington - once prayed, doctors set up a make-shift clinic following the attacks to treat the burned and bruised feet of the rescuers.
Five years later, the families of the fallen sat alongside members of the rescue teams, sharing the pews with local, state and federal officials for an interfaith memorial prayer service. President Bush sat in a front row and listened as Reverend James Cooper spoke.
"Welcome to St. Paul's Chapel, a place of respite, love and hope, a house of prayer for all people where each of us equally is a guest in this holy place," he said.
The president will mark the actual moments when the planes hit the twin towers with emergency workers at a firehouse near the World Trade Center. From New York he will travel to the Pennsylvania field where another hijacked plane was flown into the ground, and finally to the Pentagon near Washington where terrorists crashed a jetliner into the Department of Defense headquarters.
Throughout the day, the president will let others do the talking, and let the powerful images of remembrance tell the story. Mr. Bush is not expected to make any remarks until he returns to the White House late in the day, and addresses the American people.