This paper analyzes the main features of the urban reforms by Benjamin Vicuña Mackenna in Santiago de Chile between 1872 and 1875. We pay special attention to the origin of the objectives of modernization, closely related to the political agenda of Latin American elites to create an urban culture (civilization). We also analyze the strategies of social defence that these reforms implied. The influence of French positivism and the Haussmann project in Paris was very important in the Vicuña Mackenna project and its model of a segregated city: the «European city» itself, -bourgeois, civilized and hygienic-, which should be protected, and the «African township», -lower-class feral and unhygienic-, whose population must be regenerated and colonized.