Notre Dame cathedral, a treasure of French Gothic architecture, is one of the most famous symbols of Paris, attracting an estimated 13 million visitors and pilgrims yearly.
On Monday, a fire broke out at the medieval Catholic church, toppling its spire and destroying the roof.
This much-loved church was built on the Île de la Cité, a natural island in the middle of the Seine river, and for more than 850 years has been at both the physical and spiritual heart of the French capital.
Construction began in 1160, under the instruction of Bishop Maurice de Sully. A Romanesque church that had been on the site was demolished to make way for this much grander, more ambitious Gothic project.
182 years in the making
De Sully never lived to see the cathedral complete. In fact, it was 182 years before the church was finally consecrated in 1345, with the work being carried out under a succession of bishops and master builders.
One of the building's most significant innovations is its use of flying buttresses, which gave the necessary structural support for this huge stone edifice to house more than 6,000 worshipers inside.
It's also famous for its 8,000-pipe organ, one of the world's biggest, which thankfully remains intact following Monday's fire. The bell towers were also saved.
The entire wooden interior of the cathedral has been lost and the condition of the three enormous stained glass Rose Windows is, at the time of writing, uncertain.
Good times and bad
England's King Henry VI was crowned King of France in the cathedral in 1431, and Napoleon I had his coronation as Emperor there in 1804.
Notre Dame was badly damaged during the French Revolution, during which heads of statues were removed and the cathedral was used for food storage.
It was restored by architect Eugène Viollet-le-Duc in the 19th century. The cathedral's central spire, which collapsed on Monday, was added during this period.
The restoration was partly buoyed by the success of Victor Hugo's novel "The Hunchback of Notre-Dame" in 1831, which drew attention to the poor condition of the cathedral.
French President Emmanuel Macron, speaking from the scene of Monday's fire, has described the fire as a "terrible tragedy," but has promised Parisians that they will "rebuild this cathedral together."
"It is indeed one of the most incredibly beautiful and important medieval cathedrals in the world," Yaron Yarimi, a New York-based travel agent and Paris expert, said in an email to CNN.
"It is also among the five most requested sites to be visited when we organize travel to Paris for our clients." Yarimi said he was saddened by the fire. "What a tragedy unfolding right in front of our own eyes!"