Annual 9/11 remembrance event taking place at Red Rocks in Colorado

Registration was starting just after daybreak Wednesday for a popular 9/11 remembrance event at one of Colorado's most well-known landmarks. The Colorado 9/11 Stair Climb takes place every year at Red Rocks Amphitheatre and is one of several tribute events in Colorado to honor the lives lost in America in the terror attacks on Sept. 11, 2001.

"From newborns to -- I think our oldest climber ever was in his late 80s -- there are a lot of firefighters, a lot of police officers, the military and also just a lot of people from the community that want to come spend the day with us," said organizer and West Metro firefighter Shawn Duncan.

The Colorado 9/11 Stair Climb is in its 15th year. Thousands of participants gather to do nine laps around the amphitheatre, which equates to 110 floors. Each of the twin towers of the World Trade Center in New York City had that number of floors before they collapsed.

"It's a unique way to remember the events of 9/11. To go through a little bit of what the firefighters went through that day, obviously a very small piece of it," Duncan said. "But it's also just a way for us to get together and feel a sense of unity, which is hard to find these days.

Before the participants begin their walk around the venue, there was set to be a moment of silence at 8:46 a.m.