Ribbed vaults, pointed arches, and expansive stained glass define Paris's Basilica of Saint-Denis. In the 1100s, its rebuilding replaced an earlier Romanesque church and helped establish Gothic architecture—inspiring iconic cathedrals around Europe, including Notre-Dame. Now, almost 200 years after its north tower and spire were dismantled, a reconstruction effort is underway to return Saint-Denis to its former glory. Learn more about this seminal cathedral: https://on.natgeo.com/4kI6iSY | Natio