The city is observing the 10th anniversary of the 9/11 attacks Sunday at the newly opened Memorial Plaza at the site.
The ceremony also serves as the memorial's official opening. The site opens to the public Monday.
The memorial sits next to a construction project where office towers, a transportation hub and a cultural center are taking shape. The signature skyscraper, One World Trade Center, is rising quickly and will be the tallest in the country when completed.