Today marks the somber anniversary of the attacks on September 11, 2001. The Tribute in Light installation, presented six months after 9/11 in New York City’s Lower Manhattan, has shone every year since from dusk to dawn to honor those who have been killed and show the resilient spirit of New York City.

Tribute in Light is a commemorative public art installation which had its debut on March 11, 2002, conceived by five New York artists and architects, including Gustavo Bonevardi and John Bennett, and developed with the Municipal Arts Society (MAS) and Creative Time, the project came to fruition with the help of lighting designer Paul Marantz and with Michael Ahern, an events producer who passed away in 2015. The same team of producers, electricians, technicians, mechanics and stagehands brought together by Michael Ahern in 2002, come together every year to assist in the production, and in recent years, the Tribute in Light has been run by the 9/11 Museum & Memorial.

The work is assembled on the roof of the Battery Parking Garage south of the 9/11 Memorial, and features twin beams of 88 7,000-watt xenon light bulbs shining four miles into the sky. The installation is positioned into two 48-foot squares, echoing the orientation and shape of the Twin Towers. In 2011, we had the honor of being part of the lighting ceremony and got a behind the scenes look at how the lights work.

Located on the seven story concrete garage, each of the 88 lights supplied by Space Cannon are roughly the size of a refrigerator. Just before dusk on the first day, a stage hand begins unveiling the lights and switching on the power for a rehearsal. Through Sept. 11 and 12, the lights are only shut off for a certain period if only there is a certain amount of bird condensing, explained Ahern in a video for the New York Times.

But the lights otherwise continue their memorial service throughout the day and night, standing stand silent and resolute, visible for a 60-mile radius in Lower Manhattan. The installation needs no explanation or narrative. It offers up a stark reminder to remember always those who lost their lives, and remember the strength resilience of New Yorkers. While Michael Ahern sadly passed away in November 2015, his words about the memorial still ring true, “I do know that, in a heartbeat, you can change people’s mood if you change the light.”

Next, here are 10 Ways to Commemorate 9/11 in NYC and read a reflection about the day by Untapped Cities Founder, Michelle Young.