The kidnapping and killing marked a turning point in Spain's fight against the Basque separatist group.
Spain has marked the 25th anniversary of the kidnapping and murder of Partido Popular local councillor Miguel Ángel Blanco.
Authorities and citizens gathered over the weekend to honour the former Basque official, who was killed by the ETA terrorist group.
Blanco's abduction and murder shocked the whole country and marked a turning point in the fight against the armed separatist group.
The 29-year-old elected conservative councillor was kidnapped by ETA on 10 July 1997, as they called for Spain's government to transfer all ETA separatist prisoners to the northern Basque region within 48 hours.
After the government refused the "blackmail" order and despite nationwide protests calling for his release, Blanco was fatally shot and his body was left in a wasteland area. He died on July 13 in hospital.
Three former ETA leaders were charged on Friday for their alleged role in the high-profile killing.
In 2018, the terrorist group formally dissolved after four decades of violence that resulted in more than 800 deaths.
Spain's King Felipe VI and Prime Minister Pedro Sánchez were joined by the Basque regional president Iñigo Urkullu at a ceremony over the weekend in Blanco's former town, Ermua.
In his speech, Felipe VI called for unity and the so-called "Spirit of Ermua" to remember "the value of peace, life, freedom and democracy".
Spain cannot allow there to be generations "who ignore what happened in those painful days [in 1997]," he added.
PM Sánchez also announced that Spanish students would also receive "direct testimony" from the victims of terrorism to help them understand historical events.
"Something changed us forever into a different country that would never again bow down to terrorism," he said.