In order to bar the King of France's route to Rouen along the Seine Valley, Richard the Lionheart, Duke of Normandy and King of England decided to build a massive fortress on the cliff over the river near Andelys in 1196. King Philippe Auguste waited until Richard's death to besiege and conquer the fort. Nowadays, its imposing ruins, an impressive keep 8m/26ft diameter and ramparts 5m/16ft thick, make a very pleasant destination for a stroll, with the bonus of breathtaking views.