Paris (CNN) As the spire of Notre Dame collapsed onto its burning roof, Parisians recoiled in horror. The fire which ravaged their beloved cathedral felt like a dagger stuck in the city's heart.

Throughout the city, crowds of residents and tourists hugged one another as the fire raged on Monday evening, some singing hymns. Others packed the banks of the Seine across from the Gothic masterpiece, hoping against hope that some 400 firefighters could prevent further damage. Others held their heads in their hands, unable to watch.

"This can't be happening, it's breaking my heart," one woman muttered.

"Not Notre Dame. Not Notre Dame."

To Parisians, and to some 13 million visitors each year, Notre Dame is a symbol of the French capital. Its foundation stone was laid in 1163 by Pope Alexander III, and the cathedral was finally completed in the 13th century.

It withstood multiple restorations and extensions, including the addition of its central spire in the 19th century, partly buoyed by the success of Victor Hugo's novel, "The Hunchback of Notre-Dame." The building was undergoing renovation work at the time of the fire on Monday.

While the magnificent edifice with its towers, spire, flying buttresses and stained glass draws art and architecture buffs from around the world, for generations of Catholics it has also been a place of pilgrimage and prayer.

The cathedral is home to a selection of sacred relics including a fragment of the Wood of the Cross -- believed by many to be a part of the "true cross" on which Jesus was crucified -- and what is supposedly one of the nails that the Romans used to crucify him.

Notre Dame is not only a repository of historical and religious treasures, it also has a place in the hearts of many.

As the fire raged Monday evening, eyewitness Anne Marie called it a "monumental symbol." Speaking with tears in her eyes, she said the fire was a blow to every Parisian -- and to the city itself.

"Paris without the cathedral is not Paris anymore," she said.

French-American François-Xavier Lochet, 70, remembers climbing the towers of the north belfry as a 12-year-old. Now he attends Mass on his visits back to Paris. On Monday evening, Lochet was inside the cathedral when an alarm began blaring, signaling worshipers to evacuate.

Lochet, close to tears, watched billows of smoke grow and grow. Notre Dame, he said, is his "most favorite church, "constructed by countless craftsmen who devoted their lives to it."

It is "a huge piece of the history of Europe," Lochet added.

The fire destroyed the spire and most of its medieval roof, known as "the forest" because it required a forest to build it, according to Msgr. Patrick Chauvet, the rector of the cathedral.

One firefighter was seriously injured, according to Paris Fire Brigade Commander General Jean-Claude Gallet.

However, all has not been lost.

Speaking just before midnight, French President Emmanuel Macron described the fire as a "terrible tragedy," but added the "worst had been avoided."

The facade and the two main towers were declared safe.

Macron promised an international fundraising campaign to rebuild the cathedral.

"I'm telling you all tonight -- we will rebuild this cathedral together. This is probably part of the French destiny. And we will do it in the next years. Starting tomorrow, a national donation scheme will be started that will extend beyond our borders," he said, acknowledging Notre Dame's influence on the European psyche.

Sites like Notre Dame perform "a contemporary, religious role and function," said Dominic Thomas, CNN European Affairs commentator and the chair of the French Department at UCLA, "but I think they've gone way beyond that."

These sites are the "markers of a longer history, a history of conflict, of revolutions and so on," added Thomas. "No matter what one's religious faith may be, they are part of a greater identity. They are the cornerstone of not just French identity, but of what one could argue could be European identity."

It is no surprise that the French will rebuild, he said.