MADRID, Spain (CNN) -- For five years, the horrible memory has lingered in the minds of Madrid's commuters, quietly riding their trains into the heart of the city. The pain is easing, but it's a nagging ache just the same.
The rush-hour train bombings killed 191 people and wounded 1,800 others.
It was March 11, 2004, during morning rush hour, that terrorists armed with powerful bombs boarded these same commuter train lines, unleashing an onslaught that killed 191 people and wounded 1,800 others.
The attacks are the deadliest in Europe since the rise of al Qaeda. More than a year later on July 7, 2005, terrorists would stage bombings on the London transit system that killed 52 people and wounded hundreds more.
The explosives were left on the Spanish trains in sports bags and backpacks -- sometimes placed under seats -- court documents say. The terrorists got off at various stations down the line, before cell-phone timers detonated 10 bombs in quick succession on four trains at three stations.
Police dismantled another bomb that didn't explode. It provided vital clues that led to arrests. Eighteen people, mostly Islamic militants, have been convicted in the attacks. Watch more on the anniversary
Juan Carlos Garcia, an engineer who took the train later that same day, said he knows a couple whose daughter died in the attacks.
"It was very tough, especially knowing it could have been you," Garcia said. "Now, you remember it, but not the same as when it just happened."
Beata Sadecka, a regular commuter, says she rides cautiously.
"Every day, when I get on the train, I always ride in the last car," Sadecka said. "I don't know why, for safety," she added, not quite sure of her motives.
On one train, the first explosion was in a rear car and, as people ran forward to get away, they were hit by explosions in the middle cars, investigators have said.
"People remember the March 11th attacks," said Vicente Jimenez, a deputy editor with El Pais newspaper, "and while conscious that the threat continues, you have to continue with your life."
Memorial observations were scheduled throughout the day, including five minutes of silence for the victims. King Juan Carlos and Prime Minister Jose Luis Rodriguez Zapatero were not taking part in the public events. A victims group called their non-participation a slight.
But on this fifth anniversary, most commuters are just going about their business, with that nagging ache still lingering.