NEW YORK – The sixteenth anniversary of the 9/11 terrorist attack in the United States is being observed today.

Every year, memorials are held in remembrance of the thousands of lives that were lost that day.

Thousands of 9/11 victims’ relatives, survivors, rescuers and others are expected to gather Monday at the World Trade Center to remember the deadliest terror attack on American soil, according to AP.

9/11 Memorial & Museum — New York, N.Y.

An anniversary ceremony, held each year on September 11, will take place at the 9/11 Memorial Plaza at the World Trade Center. The “Tribute in Light” public art installation will shine from dusk to dawn on the night of Sept. 11. Two beams of illuminated, blue light, symbolizing the Twin Towers, reach four miles into the sky and are visible within a 60-mile radius on a clear night, reported Washington Examiner.

The Pentagon — Washington, D.C.

The Pentagon Memorial will also hold its anniversary commemoration and is the first national memorial dedicated to the terror attacks on 9/11. Each memorial unit consists of a cantilevered bench, a lighted, reflecting pool of water, and a tribute to each of the 184 Pentagon victims.

Flight 93 National Memorial — Shanksville, Pa.

This year on Sept. 10, Flight 93 National Memorial will host a “soundbreaking” for the memorial’s last element, the Tower of Voices. Once constructed, the tower will contain 40 different chimes to symbolize the eternal voices of the passengers and crew members of Flight 93, according to Washington Examiner.