Rouen’s stunning Gothic cathedral, built between the late 12th and 16th centuries, was famously the subject of a series of canvases painted by Monet at various times of the day and year. The 75m-tall Tour de Beurre (Butter Tower) was financed by locals in return for being allowed to eat butter during Lent – or so the story goes. A free sound-and-light spectacular is projected on the façade every night from June (at 11pm) to late September (at 9.30pm).
Look out for the arresting sight of the highly ornate Escalier de la Bibliothèque du Chapitre (Library Staircase); the first two flights were crafted in the 15th century, while the upper two flights were added in the 18th century.