Notre-Dame Cathedral of Paris

Notre-Dame de Paris is defined by its massive western facade, flanked by two towering square-topped bell towers that overlook the eastern end of the Île de la Cité. The limestone structure is held aloft by a skeleton of external flying buttresses, a radical engineering innovation that allowed builders to replace thick, heavy walls with expansive stained-glass rose windows. Construction began in eleven sixty-three under Bishop Maurice de Sully and continued for nearly two centuries, replacing an earlier Romanesque church built on the site of a temple to Jupiter.