9/11 Tribute in Light on 15th anniversary: See photos

The annual Tribute in Light was projected into the sky on Sunday night, marking the 15th anniversary of the Sept. 11 terrorist attacks.

The blue pillars illuminated the skyline of Lower Manhattan, reaching four miles into the sky. It is visible within a 60-mile radius when the sky is clear, according to the National September 11 Memorial & Museum.

There are 88 7,000-watt xenon light bulbs that are positioned in the shape of the Twin Towers.

See photos of the tribute below.