When you visit the medieval city of Carcassonne, you can see the Basilica of St. Nazaire and St. Celse.
Founded in 1096 on the grounds of an earlier church that may date from as far as the 6th Century. Finished in the 12th Century, it was originally of Roman style, but was enlarged in the 13th and 14th Century in gothic style and nowadays we can still see both styles cohabiting, even after Viollet-le-Duc‘s renovations.