Finding vegetarian friendly restaurants in Europe isn't too difficult. Actually, in most cities and larger towns it is quite easy. Many restaurants will indicate on the menu which items are meat-free or even vegan but some smaller towns (looking at you France) I have been served meat in dishes even after telling the waiters (in their language) that I don't eat meat. I have learned that I have to say "no chicken, no pig, no cow, no fish" for them to fully understand what no meat means. Or when in doubt I stick to pizza and cheese omelettes.
Even though I have a vegetarian diet, I am not a huge fan of "vegetarian/vegan only" restaurants.
