This is heart-breaking. Notre Dame is burning.
The cathedral is 850 years old, having been begun in the 1160s under the direction of the bishop of Paris. The pope laid the cornerstone. There had been older cathedrals there since the fourth or fifth century, changed or replaced every century or two, but this one was so large and so beautiful that it was never replaced. It's built of local limestone. The roof, now gone, was supported by wooden beams, giant oaks dating from the twelfth century, which would have been very dry and burned very readily.
It's one of the earliest and best-known churches in the Gothic style, a new twelfth-century way of building churches that emphasized height and light. (The monastery of St.-Denis, on the outskirts of Paris, is now considered the first Gothic church, a generation earlier.)
The church was finished within a generation, but of course it had challenges and issues over the centuries—though nothing like what it is now facing. The first problem was that the high walls, pierced by high windows, started bowing ever so slightly but very alarmingly. The flying buttresses were then added to help keep the walls upright at the beginning of the thirteenth century.
During the early eighteenth century, the church lost much of its medieval stained glass, knocked out by the cathedral canons as too "old fashioned." Then in the late eighteenth century, when France went officially atheistic during the Revolution, the facade was deliberately damaged, the heads knocked off the kings and queens of the Old Testament who were ranged across the front.
It was still however the biggest, most important building in Paris, and when Napoleon was crowned emperor (crowning himself), he held the ceremony in Notre Dame.
The novelist Victor Hugo deplored the dilapidated condition of the cathedral, and in his Notre Dame de Paris (1831), usually translated as The Hunchback of Notre Dame, he inspired Parisians to look at their cathedral and save it. Extensive renovations were carried out, headed by Viollet le Duc, who put new heads on the Old Testament kings and queens, added gargoyles, and had the whole thing topped off by a spire (flèche in French) at the crossing point of nave and the perpendicular aisles (transept), which spire collapsed today.
Recently the whole church was cleaned of the dirty patina from polluted air and was looking fresh and inviting, as seen in the picture below, taken the last time we were in Paris. The limestone walls still stand, but it may be an awfully long time, if ever, before the church will be itself again. (Limestone doesn't actually burn but it disintegrates in intense heat. It is burned in kilns to form one of the components of cement.)
In the twelfth century, when Chartres cathedral caught fire, the local citizens pounded on the walls and cursed God. One can see their point.
Added May 6:
Amazingly, much of the interior of the church survived. There was stone arching (ceiling) below the actual roof, and it held up fairly well. The biggest damage was at the crossing, where the nave met the transept. The nineteenth-century spire crashed through there when it fell.
But obviously the church still needs a roof. There are not 1300 oaks in Europe big enough to replace the 1300 wooden beams (made from oaks already several centuries old in the twelfth century). And there is concern that, without a roof pressing down and out, the walls, which are pushed in by the flying buttresses, might start leaning toward the center.
Here's an article from the NY Times about how the fire spread--and how it could have been even worse than it is.
The French government has promised restoration within 5 years, in time for the next Olympics (to be held in Paris). We'll see. But cathedrals have been rebuilt before. Reims, in northern Champagne, was blown up in WW I, leaving nothing but the walls, and was rebuilt back to its thirteenth-century glory over 20 years.
© C. Dale Brittain 2019