NEW YORK (AP) — Americans were commemorating 9/11 with somber tributes, volunteer projects and a new monument to victims Tuesday, after a year when two attacks demonstrated the enduring threat of terrorism in the nation’s biggest city.

Margie Miller was among the 9/11 victims’ relatives, survivors, rescuers and others who gathered on a misty Tuesday morning at the memorial plaza where the World Trade Center’s twin towers once stood. She came to the site from her home in suburban Baldwin, as she does 10 or so times a year, to remember her husband, Joel Miller. Only a few fragments of his remains were recovered.

“To me, he is here. This is my holy place,” his widow said before the ceremony began with a moment of silence and tolling bells at 8:46 a.m., the time when the trade center was hit by the first of two terrorist-piloted planes.

President Donald Trump and Vice President Mike Pence headed to the two other places where hijacked planes crashed on Sept. 11, 2001, in the deadliest terror attack on American soil.

The president and first lady Melania Trump planned to join an observance at the Sept. 11 memorial in a field near Shanksville, Pennsylvania, where a new “Tower of Voices” was dedicated Saturday. Pence is attending a ceremony at the Pentagon. Trump, a Republican and native New Yorker, took the occasion of last year’s anniversary to issue a stern warning to extremists that “America cannot be intimidated.”