Third Culture Kids: in exchange for feeling rootless and saying way too many goodbyes, most of these people turn out to be highly adaptive and resourceful adults.
Some of my favorite moments as a tour leader are watching the expressions of our travelers as they first encounter some of these wonders. There is a particular corner where I like to skip ahead just a little so I can savor the expressions as the group rounds the corner and sees the magnificent Eiffel Tower towering above them in all its glory.