There are certain cities throughout the world that we all know the names of: Paris, Tokyo, New York, Moscow. We likely know one or two things about each of these cities. Paris has the Eiffel Tower. New York has Broadway. But each city has its own, unique elements that not a lot of people know about. For example, who knew that one of Los Angeles' iconic plants actually isn't even native to the city? Or that there is a very specific traffic sign that is missing throughout all the streets of Paris? From fortresses to subway systems to green spaces, these hidden gems are some of the coolest things we've heard about these major cities. Which is your favorite?