France: What is the architectural significance of Paris' Notre-Dame cathedral?

Paris' Notre-Dame Cathedral is about to reopen, five years after a devastating fire. The 860-year-old medieval building has been meticulously restored, with a new spire and rib vaulting and its flying buttresses and carved stone gargoyles returned to their past glory. FRANCE 24's William Hilderbrandt interviews Laura O'Brien, lecturer in modern European history at Northumbria University in Newcastle-upon-Tyne, about the architectural significance of the cathedral.