The bells of all 650 churches in Madrid tolled for five minutes beginning at 7:37 a.m., when the first of the dynamite-loaded backpacks detonated on four rush-hour trains, reports CBS News Correspondent Elaine Cobbe.
King Juan Carlos and Queen Sofia led government leaders and other dignitaries during the main memorial — a silent, five-minute noon vigil inaugurating a grove of 192 olive and cypress trees, one for each person killed last March 11 and a policeman killed when Islamic militant suspects seeking to avoid arrest blew themselves up.
The grove in Madrid's main park has been christened the "Forest of the Absent."
After the vigil, a young cellist dressed in black played "Song of the Birds" by Pablo Casals, a piece the late Spanish composer and musician had dedicated to peace.
As the dignitaries stood in grim silence, much of Spain paused in remembrance. Trains made unscheduled stops at stations, and people stopped in the street to grieve over an attack that cut across nationality, killing immigrants from Ecuador to Ukraine, from France to the Philippines.
Earlier, at the rail stations targeted in the attack, people huddled together and shed tears as memories of the blasts returned. Some left notes that tried to put pain into words.
"Who will give me back my will to live, which died here a year ago?" read a letter posted on a wall at El Pozo station — the deadliest of four scenes of carnage. It was signed only Susana, a woman who said she was injured when bombs gutted a double-decker train.
"It really could have happened to any one of us. That is the truth," said Victoria Martinez Montes, a 70-year-old retiree, standing outside the Church of Saint Teresa on a clear, chilly morning in Spain's capital. "More than remember, what we should do is try to help those who survived because those who are gone are now with God."
At El Pozo, a man tossed red and white carnations and roses onto the railroad tracks.
Another, an emergency medical worker who attended to the dying the day of the attack, came wearing his uniform, a yellow jumpsuit, to pay his respects.
"I will never forget the image of what happened here," said the 42-year-old worker, who identified himself only as Paco. "I still remember the smell of gunpowder. Finding pieces of bodies on the platform. The image of a boy's head on a bench."
As he spoke, a text message beeped on his mobile phone. It was from a rescue-worker colleague and said: "A year ago they took something away from us."
Juana Leal, a middle-aged housewife who lost her husband in the El Pozo blast, said she got up early Friday to ride a train at the same time he did a year ago. "He never came back. I am bringing him flowers," she said. Leal placed a bouquet of carnations and daisies at an isolated spot on the platform. Tucked into it was a small photo of her husband.
Another person paying tribute was Maria Jesus Moreno, who was walking toward El Pozo when the bomb went off. She said she remembers seeing her neighbors running to catch the train that would later blow up around them. "I never saw them again," Moreno said, crying as she recalled the image.
On a train following the same route as the four that were bombed last year, passengers rode in silence. A free newspaper handed out to commuters featured a black front page with a picture of a candle.
"It is hard to take the train today. You think about that day. It all comes back," said one commuter, Pilar Almena, a 48-year-old chef.
Those attending the inauguration of the grove of trees included King Mohamed VI of Morocco, home to most of the 22 suspects in jail in connection with the attack.
Militants claimed responsibility for the attacks in videotapes, saying they were retaliating on al Qaeda's behalf for Spanish troops' presence in Iraq.
Socialists who opposed the war ousted the ruling conservatives in elections held three days later, with many voters accusing then Prime Minister Jose Maria Aznar of having made Spain a target for al Qaeda by backing the U.S.-led invasion. Aznar was also accused of lying to save the election by blaming the armed Basque separatist group ETA for the attacks, even after evidence of an Islamic link emerged.
The 22 people jailed over the bombings face preliminary charges of terrorism or mass murder. Fifty-two detainees have been released but are still considered suspects. A trial is not expected until late this year at the earliest.