Why Paris is organized like a giant, spiraling snail shell

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: Paris is divided into twenty administrative districts known as arrondissements, which spiral clockwise from the city center like a snail shell. While they define the city's geography and postal codes today, this unique layout was a strategic invention to avoid the social stigma of being assigned the number thirteen.

The current structure of twenty arrondissements dates back to 1860, following a major expansion of the city's jurisdiction under Emperor Napoleon III and Baron Haussmann. Before this reorganization, Paris was divided into only twelve districts. The transition required a new numbering system, which sparked immediate controversy among residents. Specifically, the people of Passy strongly objected to being placed in the 13th arrondissement, which at the time carried a jocular, negative connotation related to unmarried couples living together.

To resolve the tension, the mayor of Passy, Jean-Frédéric Possoz, proposed the now-iconic spiral pattern. By starting the numbering on the Right Bank near the Louvre and winding outward, the plan successfully placed Passy in the 16th arrondissement instead. This system remains the standard today, with the last two digits of Parisian postal codes—ranging from 75001 to 75020—indicating which district a location belongs to. While the arrondissements are still used for navigation and identity, their administrative role has evolved.

Governance in Paris is shaped by the 1982 PLM Law, which established the Council of Paris alongside twenty individual arrondissement councils. These local councils have limited powers and are composed of members elected specifically for the district, alongside city council members who sit ex officio. Recent reforms have further consolidated administration; in 2020, the first four arrondissements merged their services under the name Paris Centre. While these four districts still exist geographically, they no longer function as separate administrative or electoral sectors, reflecting the city's ongoing adaptation to modern urban needs.

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