The limestone used to build Notre Dame Cathedral “is considered some of the best in the world,” Guerry told CBS News. She said the space above and around the cathedral’s vault needs to be rebuilt, and the lateral walls need to be re-strengthened.

Originally sourced from Normandy in the 12th century, the Notre Dame stone was all quarried and assembled by hand.

“There will need to be a whole new system of quarrying the same stone (by hand) to create the homogeneous effect,” Guerry said. “It requires literally tons and tons and tons of stone. So we’re going to need the best stone masons on the planet, and we’re going to need the best quarries and access to them immediately.”