Fundamental safeguards — like firewalls or a sprinkler system — were absent by choice, to avoid altering the cathedral’s design or heighten risk by introducing electrical wiring to the most vulnerable part of the building: a network of ancient wooden beams, known as the forest, that supported the roof.

On Tuesday, President Emmanuel Macron called for unity and vowed to swiftly restore the structure. “We will rebuild Notre-Dame Cathedral, more beautiful than ever, and I want this to be finished in five years,” he said. “We can do it, and we will mobilize to do so.”

Go deeper: “It’s our roots, our history, our civilization.” Notre-Dame is the heart of France because it combines the secular, the sacred and the profane, our former Paris bureau chief writes.

Closer look: By amazing luck, many copper sculptures on the cathedral’s spire were removed for restoration just days before the blaze. The rooster that topped the spire — an unofficial symbol of France — was found in the debris.

Another angle: A crowdfunding campaign for three black churches in Louisiana that were destroyed by arson collected more than $750,000 after being shared widely on social media after the Notre-Dame fire.