How to get your bearings and navigate in such a antiquated, albeit breathtaking, labyrinth?
Once you discard your North American notion that streets should run north/south or east/west, and that blocks should be somewhat uniform in spread, you are free to embrace the genius of the arrondissements.
Technincally, arrondissements are administrative districts, each with its own mayor. We foreigners tend to think of an arrondissement as a group of neighborhoods, and each arrondissement is further divided into 4 smaller neighborhoods, or "quartiers" (similar to New Orleans' French Quarter).
Take a second glance at a map of Paris, and suddenly it appears perfectly organized. The 20 arrondissements form a clockwise spiral around the very center of Paris. That first arrondissement is called... what else, but the First Arrondissement, or "le premier arrondissement." From there, it continues in a fairly obvious fashion.
We have used the concept of the arrondissements extensively in our trip planning. From choosing where to stay (as each arrondissement has its own character, and often a corresponding name), to deciding which sites can be visited in the same day, arrondissement awareness is as essential as an 112-page map for any stay in Paris.