fiction set in Europe, plsthx

We are looking at a family trip to Europe this spring, and flailing attempting to find a theme. Around England we went with "actual places children's books we love are based on and in" and that got us the Lake district for Swallows and Amazons and Beatrix Potter, London for a handful of basic London things and also the Globe Theater, and then Stonehenge and the territory where A. A. Milne summered and wrote the Pooh stories. People! We played Poohsticks on the bridge out of the illustration and it was magic.

So we were brianstorming last night after supper and it looks like we are chasing Roman ruins, ice age humans, science museums and rando architecture/geography frex Mont St Michel. We don't do art museums gracefully, but we'll walk a lot.

Any suggestions for A) fiction to help us think about the area or B) things we might want to be sure to see? I am hoping for modern, possibly YA, not hugely depressing fiction... The two I could think of offhand are both from Hilary McKay: Saffy's Angel, that has some parts in Italy, and Exiles in Love that is at least half in France and has possibly the MOST beautiful scene of a small child communicating with shopkeepers to acquire food ever. Particualrly after her elder sisters basically had a meltdown on overload from attempting to remember what French they knew and ended up shouting "SHUT UP SHUT UP" in French at the shopkeepers. I have a lot of sympathy for all concerned in that scene.