Catedral de Auxerre

The Cathedral of Saint Etienne in Auxerre is currently Gothic, but has kept the basic features of the original building, including the crypt of the old Romanesque work. The construction of the Church was between the years 1215 and 1550 and was never finished. The South Tower was never constructed because of the slowness of the work and the religious wars and the Revolution. Aside from the cathedral, you can visit the Treasury, which has manuscripts, enamels, paints etc. I recommend to visit the Romanesque crypt dating back to the 11th century, which is what I have highlighted in this cathedral.