From the Wikipedia page 
Hauts-de-Seine (French: [o d(ə) sɛn]; literally "Heights of Seine") is a department of France. It is part of the Métropole du Grand Paris and of the Île-de-France region, and covers the western inner suburbs of Paris. It is small and densely populated and contains the modern office, theatre, and shopping complex known as La Défense.
Hauts-de-Seine and two other small départements, Seine-Saint-Denis and Val-de-Marne, form a ring around Paris, known as the Petite Couronne (i.e. "little crown") and are together with the City of Paris included in the Greater Paris since January 1, 2016.
Hauts-de-Seine is made up of three departmental arrondissements and 36 communes