the city's cathedral, a year-round destination for Roman Catholic pilgrims.
A memorial service was scheduled there for the victims on Monday, but media attention was meanwhile focussed on the driver who the government said was suspected of being to blame for the crash.
The man, Francisco Jose Garzon Amo, 52, refused to answer police questions on Friday from his hospital bed, and the case was passed to the courts.
Garzon was taken to a police station on Saturday after being discharged from hospital and was due to appear on Sunday before a judge who will decide whether to press formal charges, court officials said.
Interior minister Jorge Fernandez Diaz told reporters on Saturday that Garzon Amo faced possible charges of reckless homicide.
The train was reported to have been travelling at more than twice the speed limit on a bend when it tore off the rails on Wednesday and slammed into a concrete wall, with one carriage leaping up onto a siding.
Regional authorities say that 78 passengers died and 178 were injured in the accident, Spain's deadliest rail accident since 1944.
"We are really feeling the impact. People are praying. It is a great tragedy," said Marlen de Francisco, a local woman of 70 who sells souvenirs in the cathedral square.
"All day people are asking me for note paper so they can write messages and put them on the cathedral gates."
Regional health officials said 71 people were still in hospital, including 28 adults and three children in critical condition.
At least eight foreigners were among the dead - a US citizen, an Algerian, a Mexican, a Brazilian, a Venezuelan, an Italian, a national of the Dominican Republic and a Frenchman.
The president of the Spanish rail network administrator ADIF, Gonzalo Ferre, said Garzon had warnings to start slowing the train "four kilometres before the accident happened".
El Pais newspaper, citing investigation sources, reported that he told railway officials by radio that the train had taken the curve at 190 kilometres (118 miles) an hour - more than double the 80 kph speed limit for that section of track.
State railway company Renfe said the driver had been with the firm for 30 years, including 13 years as a driver, and had driven trains past the spot of the accident 60 times.
El Mundo newspaper on Sunday printed extracts from the train's route plan, indicating that ahead of the bend the train passed from a stretch of track with a speed limit of 220 kph to one with a limit of 80 kph.
The newspaper said it was "surprising" that it was left entirely up to the driver exactly when to brake as the train went into the curve.
Some media reports described Garzon Amo as a speed freak who once posted a picture on his Facebook page of a train speedometer at 200 kph.
But Garzon also has his defenders.
"He is an excellent professional," said Antonio Rodriguez, a UGT labour union leader who joined Renfe alongside Garzon in 1982. "It is the first accident he has ever had."
Renfe said the train - a model able to adapt between high-speed and normal tracks - had no technical problems and had just passed an inspection on the morning of the accident.
But the secretary general of Spain's train drivers' union, Juan Jesus Garcia Fraile, told public radio the track was not equipped with braking technology that would slow the train down automatically if the driver failed to so when required.
A truck carried away one of the gutted carriages from the site on Saturday and passengers' relatives collected luggage recovered from the wreck.
Many of the passengers were said to be on their way to a festival in honour of Saint James, the apostle who gave his name to Santiago de Compostela.
"As a believer, I wonder how Saint James can have allowed this to happen," said Pedro, a grey-bearded pilgrim from Cantabria in northern Spain, wearing a cape and using a walking stick.