Eugene Viollet-le-Duc is still the man to go to when it comes to restoring Notre Dame, even though he died nearly 140 years ago. As a young architect in Paris, Viollet-le-Duc made it his life's work to preserve the iconic cathedrals, monasteries and palaces that were damaged during the French Revolution and fell into further disrepair amid an early 19th century economic slump. His more than 20 years of work on Notre Dame, already prized for its vision and detail, may be put to its greatest use yet.