JEFFERSON COUNTY, Colo. -- About 2,500 people gathered at Red Rocks Park and Amphitheatre on Wednesday morning for the 11th Colorado 9/11 Memorial Stair Climb.
The annual event at the famed venue honors the 343 New York Fire Department firefighters and nearly 3,000 other people who were killed in the Sept. 11 terrorist attacks in 2001.
Several firefighters in full gear and carrying hoses and equipment simulated the trek up 110 flights of stairs -- the height of the World Trade Center twin towers.
The route goes from the upper south parking lot, up to the south ramp and around nine counter-clockwise laps in the amphitheater.
Organizers said it's the largest and most well-attended stair climb in the country, with more than 2,300 attending last year.
"I think that’s incredible," firefighter in training Josh Perl said. "Burning building. No one was handing out water. They didn’t go down the stairs, that counts. Up the whole time carrying hoses."
Everyone carries a badge for each of the firefighters who were killed at the World Trade Center.
Proceeds from the event go to the FDNY Counseling Services Unit and programs provided by the National Fallen Firefighters Foundation that supports families of fallen firefighters.