Rouen

Rouen needs 1 day: touring the Cité Immersive Viking, an audiovisual experience about the city's Norman founding by Vikings in the 9th century, and visiting the Old Market Square, where Joan of Arc was burned at the stake in 1431, the same afternoon. April-June and September-October bring the mildest weather. It's inexpensive for northern France. Its Gothic cathedral, painted by Claude Monet in over 30 canvases between 1892 and 1894, was the tallest building in the world for four years after its cast-iron spire was installed in 1876, and the city gives its name to the Normans who founded it.