President Obama addresses guests last week at the dedication of the 9/11 Memorial Museum, built amid the foundations of the fallen Twin Towers. (Carolyn Kaster / Associated Press)
Vernoy Paolini places an American flag at a name etched in a plaque beside of the waterfalls and reflecting pools at the 9/11 Memorial. (Spencer Platt / Getty Images)
A flag and rose left in tribute at the 9/11 Memorial. (Spencer Platt / Getty Images)
One of the waterfalls and reflecting pools at the 9/11 Memorial. The adjacent 9/11 Memorial Museum opened Wednesday. (Spencer Platt / Getty Images)
Freedom Tower, rising 1,776 feet to replace the fallen Twin Towers, as seen from ground level at the 9/11 Memorial. (Spencer Platt / Getty Images)
Six months after the attacks, in March 2002, the World Trade Center site was still an open wound. (Mark Lennihan / Associated Press)
