Reconstructing.

The restoration efforts at Notre-Dame continue using ancient tools and techniques ...

"Working inside the massive wooden structure was extremely impressive," he says. "You're in the sky but completely in the dark, so you discovered 'the forest' with flashlight and headlamps, never entirely seeing the whole thing. But you could hear and feel everything going on in the cathedral below — the priests celebrating Mass, the smell of incense. And we were near the belfry, so all of a sudden the bells would ring and resound very strongly. It was as if the cathedral was alive under your feet."

It is thanks to those plans that today's builders know exactly how to reconstruct the charpente, says Fromont. And there are several reasons to rebuild the Gothic masterpiece exactly as it was.

"A cathedral is a structural ensemble that's very complex, and as soon as you change one little thing, one parameter, it impacts everywhere else in the cathedral," he says. "So reconstructing it exactly the same way is also a precaution. It worked very well for 800 years. So we know if we build it back the same way we won't risk damaging the cathedral by trying something new."