Flames and smoke are seen billowing from the roof at Notre-Dame Cathedral in Paris on April 15, 2019. - A fire broke out at the landmark Notre-Dame Cathedral in central Paris, potentially involving renovation works being carried out at the site, the fire service said.Images posted on social media showed flames and huge clouds of smoke billowing above the roof of the gothic cathedral, the most visited historic monument in Europe. (Photo by LUDOVIC MARIN / AFP)