Without Borders - Mont Saint-Michel Castle
Great building or actually village. It's immense. Been there once on a holiday to the French west coast.
Sorry, not to spoil your fun, but I think you're supposed to look for buildings or architecture within your own country. I want to join to and still haven't decide yet on a building in the Netherlands. So before you finish the model I think you should check with the jury 😉
Best of luck.