The City of Paris is divided into twenty arrondissements municipaux, administrative districts, more simply referred to as arrondissements (aʁɔ̃dismɑ̃). These are not to be confused with departmental arrondissements, which subdivide the larger French departments.
The number of the arrondissement is indicated by the last two digits in most Parisian postal codes (75001 up to 75020). In addition to their number, each arrondissement also has a name, often for a local monument. For example, the 5th arrondissement is also called "Panthéon" in reference to the eponymous building. The first four arrondissements have a shared administration, called Paris Centre.
The twenty arrondissements (French: "rounding") are arranged in the form of a clockwise spiral (often likened to a snail shell), starting from the middle of the city, with the first on the Right Bank (north bank) of the Seine.
In French, notably on street signs, the number is often given in Roman numerals. For example, the Eiffel Tower belongs to the VIIe arrondissement while Gare de l'Est is in the Xe arrondissement. In daily speech, people use only the ordinal number corresponding to the arrondissement, e.g. "Elle habite dans le sixième", "She lives in the 6th (arrondissement)".
Due to suburbanization, the population of Paris has gradually shifted outward, with only two arrondissements still growing.
Council of Paris
Uniquely among French cities, Paris is both a municipality (commune) and a department (département). Under the PLM Law (Loi PLM) of 1982, which redefined the governance of Paris, Lyon, and Marseille (hence the PLM acronym), there are both a city council called the Council of Paris and 20 arrondissement councils in Paris. The PLM Law also set limits to the prerogatives of the mayor of Paris, who has to deal with the powers granted to the prefect of police on security issues.
The 20 arrondissement councils (conseils d'arrondissement) are similar in operation to a municipal council (conseil municipal) but with very few powers.