Cops, firefighters and armed-services veterans were among those who laced up Sunday to follow in the footsteps of a fallen city hero.

The group honored the heroism of 9/11 first-responder Stephen Siller by partaking in the 18th annual Tunnel to Towers 5K race, which goes from the Brooklyn Battery Tunnel to the World Trade Center in Lower Manhattan.

Around 30,000 runners and walkers retraced the route that the fallen firefighter took before he lost his life on 9/11.

“It’s really inspiring to see the whole community come together for this race — firemen, police officers, the army,” said participant Jarley Patel, a first-year West Point cadet. “It really encompasses what it means to be American.”

Marine veteran Mark Zambon, who lost his legs in Afghanistan, also was among those who participated in the race. The former member of the Marines’ bomb-disposal unit came from Sacramento, Calif., to cross the finish line using prostheses.

“It’s really special, to follow the footsteps Stephen Siller took on Sept. 11, what he was preparing mentally for and what he did,” Zambon said. “It’s a very moving thing to be a part of it and to see a show of such support from the whole community of first responders and soldiers. To know we are all in this together as brothers and sisters is a very special thing.”

NYPD Detective Theresa Diaz said it can be emotional and “surreal” to see everyone come together for the race.

“Just seeing all the NYPD, firemen, the military, you see all the sacrifice — you realize that freedom isn’t free,” Diaz said.