Mantes-la-Jolie and Château de La Roche-Guyon from Paris

This day trip pairs two lesser-known gems of the Île-de-France into a rewarding escape from Paris. In Mantes-la-Jolie, the Collegiate Church of Notre-Dame — nicknamed the Little Sister of Notre-Dame de Paris — impresses with its 9-metre rose window and rare Merklin symphonic organ, while the neighbouring Hôtel-Dieu Museum holds Europe's largest collection of Neo-Impressionist painter Maximilien Luce. From there, the route continues to the village of La Roche-Guyon, where a thousand-year-old château clings to a chalk cliff above the Seine — climb 270 steps through a secret underground passage to the medieval keep for sweeping views of the Vexin countryside. A restored 18th-century kitchen garden and Rommel's WWII bunkers carved into the cliff round out this layered journey through French history. Note that the château is open only from April to November, and both sites in Mantes-la-Jolie close on Tuesdays.