In London I used to go to any location of Paul -- I frequented the one in Covent Garden -- for their pain au chocolat and croissant and their cakes and sandwiches.

In Paris, Pierre Herme in the Rive Gauche had THE best iterations of both croissant and pain au chocolat I had. However, almost any bakery in Paris makes a very good croissant.

In Japan, in the basement of virtually every department store is a food hall and there is almost always a bakery. The higher the quality department store, typically higher quality bakery.