You always hear about the seven hills of Rome but what about the seven hills of Paris? This reports on my scientific study of the Parisian hills, based on the Vélib’ bicycle sharing system. High-elevation Vélib’ stations are designated with a “+” sign, indicating that you will get a credit if you ride a bicycle up there from a lower-elevation station. This is important because the natural tendancy is to coast down but not struggle back up. The Vélib’ iOS app shows the location of all stations, et voila !
There are, of course, less rigorously scientific ways of categorizing the Paris hills, such as this Wikipedia item: Topography of Paris.