The Avenue Circulaire, which surrounds the observatory built in 1883, was at the end of the 19th century mainly a resort area with quite wealthy villas. Urbanization resumed after the Première Guerre World War to intensify in the 50s. We will thus discover the director's house of the Observatory, in an academic style inspired by Italian classicism, an Art Nouveau school, a magnificent modernist telephone exchange completely glazed, as well as several houses incorporating the alphabet of 20th-century architectural styles.